drm/amd/display: fix incompatible structure layouts

Submitted by Arnd Bergmann on Feb. 2, 2018, 12:31 p.m.

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Message ID 20180202123232.477388-1-arnd@arndb.de
State New
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Series "drm/amd/display: fix incompatible structure layouts" ( rev: 1 ) in DRI devel

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Commit Message

Arnd Bergmann Feb. 2, 2018, 12:31 p.m.
Building the amd display driver with link-time optimizations revealed a bug
that caused dal_cmd_tbl_helper_dce80_get_table() and
dal_cmd_tbl_helper_dce110_get_table() get called with an incompatible
return type between the two callers in command_table_helper.c and
command_table_helper2.c:

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.h:31: error: type of 'dal_cmd_tbl_helper_dce80_get_table' does not match original declaration [-Werror=lto-type-mismatch]
 const struct command_table_helper *dal_cmd_tbl_helper_dce80_get_table(void);

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.c:351: note: 'dal_cmd_tbl_helper_dce80_get_table' was previously declared here
 const struct command_table_helper *dal_cmd_tbl_helper_dce80_get_table(void)

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.h:32: error: type of 'dal_cmd_tbl_helper_dce110_get_table' does not match original declaration [-Werror=lto-type-mismatch]
 const struct command_table_helper *dal_cmd_tbl_helper_dce110_get_table(void);

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.c:361: note: 'dal_cmd_tbl_helper_dce110_get_table' was previously declared here
 const struct command_table_helper *dal_cmd_tbl_helper_dce110_get_table(void)

The two versions of the structure are obviously derived from the same
one, but have diverged over time, before they got added to the kernel.

This moves the structure to a new shared header file and uses the superset
of the members, to ensure the interfaces are all compatible.

Fixes: ae79c310b1a6 ("drm/amd/display: Add DCE12 bios parser support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 .../drm/amd/display/dc/bios/command_table_helper.h | 33 +----------
 .../amd/display/dc/bios/command_table_helper2.h    | 30 +---------
 .../display/dc/bios/command_table_helper_struct.h  | 66 ++++++++++++++++++++++
 3 files changed, 68 insertions(+), 61 deletions(-)
 create mode 100644 drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h
index 1fab634b66be..4c3789df253d 100644
--- a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h
+++ b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h
@@ -29,38 +29,7 @@ 
 #include "dce80/command_table_helper_dce80.h"
 #include "dce110/command_table_helper_dce110.h"
 #include "dce112/command_table_helper_dce112.h"
-
-struct command_table_helper {
-	bool (*controller_id_to_atom)(enum controller_id id, uint8_t *atom_id);
-	uint8_t (*encoder_action_to_atom)(
-			enum bp_encoder_control_action action);
-	uint32_t (*encoder_mode_bp_to_atom)(enum signal_type s,
-			bool enable_dp_audio);
-	bool (*engine_bp_to_atom)(enum engine_id engine_id,
-			uint32_t *atom_engine_id);
-	void (*assign_control_parameter)(
-			const struct command_table_helper *h,
-			struct bp_encoder_control *control,
-			DIG_ENCODER_CONTROL_PARAMETERS_V2 *ctrl_param);
-	bool (*clock_source_id_to_atom)(enum clock_source_id id,
-			uint32_t *atom_pll_id);
-	bool (*clock_source_id_to_ref_clk_src)(
-			enum clock_source_id id,
-			uint32_t *ref_clk_src_id);
-	uint8_t (*transmitter_bp_to_atom)(enum transmitter t);
-	uint8_t (*encoder_id_to_atom)(enum encoder_id id);
-	uint8_t (*clock_source_id_to_atom_phy_clk_src_id)(
-			enum clock_source_id id);
-	uint8_t (*signal_type_to_atom_dig_mode)(enum signal_type s);
-	uint8_t (*hpd_sel_to_atom)(enum hpd_source_id id);
-	uint8_t (*dig_encoder_sel_to_atom)(enum engine_id engine_id);
-	uint8_t (*phy_id_to_atom)(enum transmitter t);
-	uint8_t (*disp_power_gating_action_to_atom)(
-			enum bp_pipe_control_action action);
-	bool (*dc_clock_type_to_atom)(enum bp_dce_clock_type id,
-			uint32_t *atom_clock_type);
-    uint8_t (*transmitter_color_depth_to_atom)(enum transmitter_color_depth id);
-};
+#include "command_table_helper_struct.h"
 
 bool dal_bios_parser_init_cmd_tbl_helper(const struct command_table_helper **h,
 	enum dce_version dce);
diff --git a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h
index 9f587c91d843..785fcb20a1b9 100644
--- a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h
+++ b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h
@@ -29,35 +29,7 @@ 
 #include "dce80/command_table_helper_dce80.h"
 #include "dce110/command_table_helper_dce110.h"
 #include "dce112/command_table_helper2_dce112.h"
-
-struct command_table_helper {
-	bool (*controller_id_to_atom)(enum controller_id id, uint8_t *atom_id);
-	uint8_t (*encoder_action_to_atom)(
-			enum bp_encoder_control_action action);
-	uint32_t (*encoder_mode_bp_to_atom)(enum signal_type s,
-			bool enable_dp_audio);
-	bool (*engine_bp_to_atom)(enum engine_id engine_id,
-			uint32_t *atom_engine_id);
-	bool (*clock_source_id_to_atom)(enum clock_source_id id,
-			uint32_t *atom_pll_id);
-	bool (*clock_source_id_to_ref_clk_src)(
-			enum clock_source_id id,
-			uint32_t *ref_clk_src_id);
-	uint8_t (*transmitter_bp_to_atom)(enum transmitter t);
-	uint8_t (*encoder_id_to_atom)(enum encoder_id id);
-	uint8_t (*clock_source_id_to_atom_phy_clk_src_id)(
-			enum clock_source_id id);
-	uint8_t (*signal_type_to_atom_dig_mode)(enum signal_type s);
-	uint8_t (*hpd_sel_to_atom)(enum hpd_source_id id);
-	uint8_t (*dig_encoder_sel_to_atom)(enum engine_id engine_id);
-	uint8_t (*phy_id_to_atom)(enum transmitter t);
-	uint8_t (*disp_power_gating_action_to_atom)(
-			enum bp_pipe_control_action action);
-	bool (*dc_clock_type_to_atom)(enum bp_dce_clock_type id,
-			uint32_t *atom_clock_type);
-	uint8_t (*transmitter_color_depth_to_atom)(
-			enum transmitter_color_depth id);
-};
+#include "command_table_helper_struct.h"
 
 bool dal_bios_parser_init_cmd_tbl_helper2(const struct command_table_helper **h,
 	enum dce_version dce);
diff --git a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h
new file mode 100644
index 000000000000..1f2c0a3f06f9
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h
@@ -0,0 +1,66 @@ 
+/*
+ * Copyright 2012-15 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: AMD
+ *
+ */
+
+#ifndef __DAL_COMMAND_TABLE_HELPER_STRUCT_H__
+#define __DAL_COMMAND_TABLE_HELPER_STRUCT_H__
+
+#include "dce80/command_table_helper_dce80.h"
+#include "dce110/command_table_helper_dce110.h"
+#include "dce112/command_table_helper_dce112.h"
+
+struct _DIG_ENCODER_CONTROL_PARAMETERS_V2;
+struct command_table_helper {
+	bool (*controller_id_to_atom)(enum controller_id id, uint8_t *atom_id);
+	uint8_t (*encoder_action_to_atom)(
+			enum bp_encoder_control_action action);
+	uint32_t (*encoder_mode_bp_to_atom)(enum signal_type s,
+			bool enable_dp_audio);
+	bool (*engine_bp_to_atom)(enum engine_id engine_id,
+			uint32_t *atom_engine_id);
+	void (*assign_control_parameter)(
+			const struct command_table_helper *h,
+			struct bp_encoder_control *control,
+			struct _DIG_ENCODER_CONTROL_PARAMETERS_V2 *ctrl_param);
+	bool (*clock_source_id_to_atom)(enum clock_source_id id,
+			uint32_t *atom_pll_id);
+	bool (*clock_source_id_to_ref_clk_src)(
+			enum clock_source_id id,
+			uint32_t *ref_clk_src_id);
+	uint8_t (*transmitter_bp_to_atom)(enum transmitter t);
+	uint8_t (*encoder_id_to_atom)(enum encoder_id id);
+	uint8_t (*clock_source_id_to_atom_phy_clk_src_id)(
+			enum clock_source_id id);
+	uint8_t (*signal_type_to_atom_dig_mode)(enum signal_type s);
+	uint8_t (*hpd_sel_to_atom)(enum hpd_source_id id);
+	uint8_t (*dig_encoder_sel_to_atom)(enum engine_id engine_id);
+	uint8_t (*phy_id_to_atom)(enum transmitter t);
+	uint8_t (*disp_power_gating_action_to_atom)(
+			enum bp_pipe_control_action action);
+	bool (*dc_clock_type_to_atom)(enum bp_dce_clock_type id,
+			uint32_t *atom_clock_type);
+	uint8_t (*transmitter_color_depth_to_atom)(enum transmitter_color_depth id);
+};
+
+#endif

Comments

On 2018-02-02 07:31 AM, Arnd Bergmann wrote:
> Building the amd display driver with link-time optimizations revealed a bug

Curious how I'd go about building with link-time optimizations.

> that caused dal_cmd_tbl_helper_dce80_get_table() and
> dal_cmd_tbl_helper_dce110_get_table() get called with an incompatible
> return type between the two callers in command_table_helper.c and
> command_table_helper2.c:
> 
> drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.h:31: error: type of 'dal_cmd_tbl_helper_dce80_get_table' does not match original declaration [-Werror=lto-type-mismatch]
>  const struct command_table_helper *dal_cmd_tbl_helper_dce80_get_table(void);
> 
> drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.c:351: note: 'dal_cmd_tbl_helper_dce80_get_table' was previously declared here
>  const struct command_table_helper *dal_cmd_tbl_helper_dce80_get_table(void)
> 
> drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.h:32: error: type of 'dal_cmd_tbl_helper_dce110_get_table' does not match original declaration [-Werror=lto-type-mismatch]
>  const struct command_table_helper *dal_cmd_tbl_helper_dce110_get_table(void);
> 
> drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.c:361: note: 'dal_cmd_tbl_helper_dce110_get_table' was previously declared here
>  const struct command_table_helper *dal_cmd_tbl_helper_dce110_get_table(void)
> 
> The two versions of the structure are obviously derived from the same
> one, but have diverged over time, before they got added to the kernel.
> 
> This moves the structure to a new shared header file and uses the superset
> of the members, to ensure the interfaces are all compatible.
> 
> Fixes: ae79c310b1a6 ("drm/amd/display: Add DCE12 bios parser support")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Thanks for the fix.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> ---
>  .../drm/amd/display/dc/bios/command_table_helper.h | 33 +----------
>  .../amd/display/dc/bios/command_table_helper2.h    | 30 +---------
>  .../display/dc/bios/command_table_helper_struct.h  | 66 ++++++++++++++++++++++
>  3 files changed, 68 insertions(+), 61 deletions(-)
>  create mode 100644 drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h
> index 1fab634b66be..4c3789df253d 100644
> --- a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h
> +++ b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper.h
> @@ -29,38 +29,7 @@
>  #include "dce80/command_table_helper_dce80.h"
>  #include "dce110/command_table_helper_dce110.h"
>  #include "dce112/command_table_helper_dce112.h"
> -
> -struct command_table_helper {
> -	bool (*controller_id_to_atom)(enum controller_id id, uint8_t *atom_id);
> -	uint8_t (*encoder_action_to_atom)(
> -			enum bp_encoder_control_action action);
> -	uint32_t (*encoder_mode_bp_to_atom)(enum signal_type s,
> -			bool enable_dp_audio);
> -	bool (*engine_bp_to_atom)(enum engine_id engine_id,
> -			uint32_t *atom_engine_id);
> -	void (*assign_control_parameter)(
> -			const struct command_table_helper *h,
> -			struct bp_encoder_control *control,
> -			DIG_ENCODER_CONTROL_PARAMETERS_V2 *ctrl_param);
> -	bool (*clock_source_id_to_atom)(enum clock_source_id id,
> -			uint32_t *atom_pll_id);
> -	bool (*clock_source_id_to_ref_clk_src)(
> -			enum clock_source_id id,
> -			uint32_t *ref_clk_src_id);
> -	uint8_t (*transmitter_bp_to_atom)(enum transmitter t);
> -	uint8_t (*encoder_id_to_atom)(enum encoder_id id);
> -	uint8_t (*clock_source_id_to_atom_phy_clk_src_id)(
> -			enum clock_source_id id);
> -	uint8_t (*signal_type_to_atom_dig_mode)(enum signal_type s);
> -	uint8_t (*hpd_sel_to_atom)(enum hpd_source_id id);
> -	uint8_t (*dig_encoder_sel_to_atom)(enum engine_id engine_id);
> -	uint8_t (*phy_id_to_atom)(enum transmitter t);
> -	uint8_t (*disp_power_gating_action_to_atom)(
> -			enum bp_pipe_control_action action);
> -	bool (*dc_clock_type_to_atom)(enum bp_dce_clock_type id,
> -			uint32_t *atom_clock_type);
> -    uint8_t (*transmitter_color_depth_to_atom)(enum transmitter_color_depth id);
> -};
> +#include "command_table_helper_struct.h"
>  
>  bool dal_bios_parser_init_cmd_tbl_helper(const struct command_table_helper **h,
>  	enum dce_version dce);
> diff --git a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h
> index 9f587c91d843..785fcb20a1b9 100644
> --- a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h
> +++ b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper2.h
> @@ -29,35 +29,7 @@
>  #include "dce80/command_table_helper_dce80.h"
>  #include "dce110/command_table_helper_dce110.h"
>  #include "dce112/command_table_helper2_dce112.h"
> -
> -struct command_table_helper {
> -	bool (*controller_id_to_atom)(enum controller_id id, uint8_t *atom_id);
> -	uint8_t (*encoder_action_to_atom)(
> -			enum bp_encoder_control_action action);
> -	uint32_t (*encoder_mode_bp_to_atom)(enum signal_type s,
> -			bool enable_dp_audio);
> -	bool (*engine_bp_to_atom)(enum engine_id engine_id,
> -			uint32_t *atom_engine_id);
> -	bool (*clock_source_id_to_atom)(enum clock_source_id id,
> -			uint32_t *atom_pll_id);
> -	bool (*clock_source_id_to_ref_clk_src)(
> -			enum clock_source_id id,
> -			uint32_t *ref_clk_src_id);
> -	uint8_t (*transmitter_bp_to_atom)(enum transmitter t);
> -	uint8_t (*encoder_id_to_atom)(enum encoder_id id);
> -	uint8_t (*clock_source_id_to_atom_phy_clk_src_id)(
> -			enum clock_source_id id);
> -	uint8_t (*signal_type_to_atom_dig_mode)(enum signal_type s);
> -	uint8_t (*hpd_sel_to_atom)(enum hpd_source_id id);
> -	uint8_t (*dig_encoder_sel_to_atom)(enum engine_id engine_id);
> -	uint8_t (*phy_id_to_atom)(enum transmitter t);
> -	uint8_t (*disp_power_gating_action_to_atom)(
> -			enum bp_pipe_control_action action);
> -	bool (*dc_clock_type_to_atom)(enum bp_dce_clock_type id,
> -			uint32_t *atom_clock_type);
> -	uint8_t (*transmitter_color_depth_to_atom)(
> -			enum transmitter_color_depth id);
> -};
> +#include "command_table_helper_struct.h"
>  
>  bool dal_bios_parser_init_cmd_tbl_helper2(const struct command_table_helper **h,
>  	enum dce_version dce);
> diff --git a/drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h
> new file mode 100644
> index 000000000000..1f2c0a3f06f9
> --- /dev/null
> +++ b/drivers/gpu/drm/amd/display/dc/bios/command_table_helper_struct.h
> @@ -0,0 +1,66 @@
> +/*
> + * Copyright 2012-15 Advanced Micro Devices, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + * Authors: AMD
> + *
> + */
> +
> +#ifndef __DAL_COMMAND_TABLE_HELPER_STRUCT_H__
> +#define __DAL_COMMAND_TABLE_HELPER_STRUCT_H__
> +
> +#include "dce80/command_table_helper_dce80.h"
> +#include "dce110/command_table_helper_dce110.h"
> +#include "dce112/command_table_helper_dce112.h"
> +
> +struct _DIG_ENCODER_CONTROL_PARAMETERS_V2;
> +struct command_table_helper {
> +	bool (*controller_id_to_atom)(enum controller_id id, uint8_t *atom_id);
> +	uint8_t (*encoder_action_to_atom)(
> +			enum bp_encoder_control_action action);
> +	uint32_t (*encoder_mode_bp_to_atom)(enum signal_type s,
> +			bool enable_dp_audio);
> +	bool (*engine_bp_to_atom)(enum engine_id engine_id,
> +			uint32_t *atom_engine_id);
> +	void (*assign_control_parameter)(
> +			const struct command_table_helper *h,
> +			struct bp_encoder_control *control,
> +			struct _DIG_ENCODER_CONTROL_PARAMETERS_V2 *ctrl_param);
> +	bool (*clock_source_id_to_atom)(enum clock_source_id id,
> +			uint32_t *atom_pll_id);
> +	bool (*clock_source_id_to_ref_clk_src)(
> +			enum clock_source_id id,
> +			uint32_t *ref_clk_src_id);
> +	uint8_t (*transmitter_bp_to_atom)(enum transmitter t);
> +	uint8_t (*encoder_id_to_atom)(enum encoder_id id);
> +	uint8_t (*clock_source_id_to_atom_phy_clk_src_id)(
> +			enum clock_source_id id);
> +	uint8_t (*signal_type_to_atom_dig_mode)(enum signal_type s);
> +	uint8_t (*hpd_sel_to_atom)(enum hpd_source_id id);
> +	uint8_t (*dig_encoder_sel_to_atom)(enum engine_id engine_id);
> +	uint8_t (*phy_id_to_atom)(enum transmitter t);
> +	uint8_t (*disp_power_gating_action_to_atom)(
> +			enum bp_pipe_control_action action);
> +	bool (*dc_clock_type_to_atom)(enum bp_dce_clock_type id,
> +			uint32_t *atom_clock_type);
> +	uint8_t (*transmitter_color_depth_to_atom)(enum transmitter_color_depth id);
> +};
> +
> +#endif
>
On Fri, Feb 2, 2018 at 4:39 PM, Harry Wentland <harry.wentland@amd.com> wrote:
> On 2018-02-02 07:31 AM, Arnd Bergmann wrote:
>> Building the amd display driver with link-time optimizations revealed a bug
>
> Curious how I'd go about building with link-time optimizations.

I got the idea from last week's LWN article on the topic, see
https://lwn.net/Articles/744507/. I needed the latest gcc version to
avoid some compiler bugs, and a few dozen kernel patches on top
to get a clean build in random configurations (posted them all today).

Most normal configurations probably work out of the box, but I have
not actually tried running any ;-)

       Arnd
On 2018-02-02 11:02 AM, Arnd Bergmann wrote:
> On Fri, Feb 2, 2018 at 4:39 PM, Harry Wentland <harry.wentland@amd.com> wrote:
>> On 2018-02-02 07:31 AM, Arnd Bergmann wrote:
>>> Building the amd display driver with link-time optimizations revealed a bug
>>
>> Curious how I'd go about building with link-time optimizations.
> 
> I got the idea from last week's LWN article on the topic, see
> https://lwn.net/Articles/744507/. I needed the latest gcc version to
> avoid some compiler bugs, and a few dozen kernel patches on top
> to get a clean build in random configurations (posted them all today).
> 
> Most normal configurations probably work out of the box, but I have
> not actually tried running any ;-)
> 

Thanks. Learn something new every day. I like this bit from the article:

> So it is basically just like if it concatenated all source files into a single one and made everything static.

Probably not a bad idea to think that way when doing kernel development. :)

Harry

>        Arnd
>