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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[ideasonboard.com,linux.intel.com,kernel.org,gmail.com,ffwll.ch]; RCPT_COUNT_TWELVE(0.00)[21]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[163.com,gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[lists.freedesktop.org,lists.infradead.org,vger.kernel.org,lists.linux.dev,lists.xenproject.org,ideasonboard.com,163.com]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:mid] X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" Hi Am 15.01.25 um 13:06 schrieb Tomi Valkeinen: > Hi, > > On 15/01/2025 13:37, Thomas Zimmermann wrote: >> Hi >> >> >> Am 15.01.25 um 11:58 schrieb Tomi Valkeinen: >> [...] >>>> These are all good points. Did you read my discussion with Andy on >>>> patch 2? I think it resolves all the points you have. The current >>>> CREATE_DUMB >>> >>> I had missed the discussion, and, indeed, the patch you attached >>> fixes the problem on Xilinx. >> >> Great. Thanks for testing. >> >>> >>>> ioctl is unsuited for anything but the simple RGB formats. The bpp >>> >>> It's a bit difficult to use, but is it really unsuited? >>> bitsperpixel, width and height do give an exact pitch and size, do >>> they not? It does require the userspace to handle the subsampling >>> and planes, though, so far from perfect. >> >> The bpp value sets the number of bits per pixel; except for bpp==15 >> (XRGB1555), where it sets the color depth. OR bpp is the color depth; >> except for bpp==32 (XRGB8888), where it is the number of bits per >> pixel. It's therefore best to interpret it like a color-mode enum. > > Ah, right... That's horrible =). > > And I assume it's not really possible to define the bpp to mean bits > per pixel, except for a few special cases like 15? > > Why do we even really care about color depth here? We're just > allocating memory. Doesn't DIV_ROUND_UP(args->bpp, SZ_8) work fine for > XRGB1555 too? Drivers always did that, but it does not work correctly for (bpp < 8). As we already have helpers to deal with bpp, it makes sense to use them.  This also aligns dumb buffers with the kernel's video= parameter, which as the same odd semantics. The fallback that uses bpp directly will hopefully be the exception. > >>> So, I'm all for a new ioctl, but I don't right away see why the >>> current ioctl couldn't be used. Which makes me wonder about the >>> drm_warn() in your patch, and the "userspace throws in arbitrary >>> values for bpp and relies on the kernel to figure it out". Maybe I'm >>> missing something here. >> >> I was unsure about the drm_warn() as well. It's not really wrong to >> have odd bpp values, but handing in an unknown bpp value might point >> to a user-space error. At least there should be a drm_dbg(). >> >>> >>>> parameter is not very precise. The solution would be a new ioctl >>>> call that receives the DRM format and returns a buffer for each >>>> individual plane. >>> >>> Yes, I think that makes sense. That's a long road, though =). So my >>> question is, is CREATE_DUMB really unsuitable for other than simple >>> RGB formats, or can it be suitable if we just define how the >>> userspace should use it for multiplanar, subsampled formats? >> >> That would duplicate format and hardware information in user-space. Some > > But we already have that, don't we? We have drivers and userspace that > support, say, NV12 via dumb buffers. But (correct me if I'm wrong) we > don't document how CREATE_DUMB has to be used to allocate multiplanar > subsampled buffers, so the userspace devs have to "guess". Yeah, there are constrains in the scanline and buffer alignments and orientation. And if we say that bpp==12 means NV12, it will be a problem for all other cases where bpp==12 makes sense. Best regards Thomas > >> hardware might have odd per-plane limitations that only the driver >> knows about. For example, there's another discussion on dri-devel >> about pitch- alignment requirements of DRM_FORMAT_MOD_LINEAR on >> various hardware. That affects dumb buffers as well. I don't think >> that there's an immediate need for a CREATE_DUMB2, but it seems worth >> to keep in mind. > > Yes, the current CREATE_DUMB can't cover all the hardware. We do need > CREATE_DUMB2, sooner or later. I just hope we can define and document > a set of rules that allows using CREATE_DUMB for the cases where it > sensibly works (and is already being used). > >  Tomi > -- -- 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)