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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[gmail.com,lists.freedesktop.org]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; RCVD_TLS_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,bootlin.com:url] X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" Hi Am 14.01.25 um 14:46 schrieb Thomas Zimmermann: > Hi > > > Am 15.12.24 um 21:53 schrieb Marek Olšák: >> The comment explains the problem with DRM_FORMAT_MOD_LINEAR. >> >> Signed-off-by: Marek Olšák >> >> diff --git a/include/uapi/drm/drm_fourcc.h >> b/include/uapi/drm/drm_fourcc.h >> index 78abd819fd62e..8ec4163429014 100644 >> --- a/include/uapi/drm/drm_fourcc.h >> +++ b/include/uapi/drm/drm_fourcc.h >> @@ -484,9 +484,27 @@ extern "C" { >>   * modifier (e.g. not setting DRM_MODE_FB_MODIFIERS in the >> DRM_ADDFB2 ioctl), >>   * which tells the driver to also take driver-internal information >> into account >>   * and so might actually result in a tiled framebuffer. >> + * >> + * WARNING: >> + * There are drivers out there that expose DRM_FORMAT_MOD_LINEAR, >> but only >> + * support a certain pitch alignment and can't import images with >> this modifier >> + * if the pitch alignment isn't exactly the one supported. They can >> however >> + * allocate images with this modifier and other drivers can import >> them only >> + * if they support the same pitch alignment. Thus, >> DRM_FORMAT_MOD_LINEAR is >> + * fundamentically incompatible across devices and is the only >> modifier that >> + * has a chance of not working. The PITCH_ALIGN modifiers should be >> used >> + * instead. >>   */ >>  #define DRM_FORMAT_MOD_LINEAR  fourcc_mod_code(NONE, 0) >> >> +/* Linear layout modifiers with an explicit pitch alignment in bytes. >> + * Exposing this modifier requires that the pitch alignment is exactly >> + * the number in the definition. >> + */ >> +#define DRM_FORMAT_MOD_LINEAR_PITCH_ALIGN_64B fourcc_mod_code(NONE, 1) > > I recently went through drivers and tried to harmonize some > pitch-related code. There are essentially all cases from 2 to 256. See > my series at > >   https://patchwork.freedesktop.org/series/141168/ > > Sometimes the driver computes the pitch requirements from the > bit-per-pixels. [1] > > Hardware also has alignment requirements for framebuffer width > (usually 8 pixels). To clarify: given this and the overall discussion here, it seems to me that modifiers and descriptors really don't fit well to the problem. Best regards Thomas > > Best regards > Thomas > > [1] > https://elixir.bootlin.com/linux/v6.12.6/source/drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c#L410 > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)