From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 96ABA47142F for ; Tue, 21 Jul 2026 23:48:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784677691; cv=none; b=P2LZez5yRgiYWUPKqG8gxw3xOBZy5/Tj+YEIWPLm2Z3gxdSb9W45UJvoF40BwVgzBequyr+r02pA2sV7cJnwpyihVa5cgFe9U4Lsnlz/Li8A+0LlhvboElHDZyrZs9AdF64RXm+I+HeTGNrI9RiZUj7ygxnTSU1MoaPiiWVOpbk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784677691; c=relaxed/simple; bh=anmdJ/g6Un1b2QdrSo/17jlBIeaVjevTHmr3nK8/njs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZaHuWq6JnoQC4qij3ohc7WK2PO7xfrS2L2L03yYB9LD5ME4LsADeZ0hnMQL+zkgc4r0/MESq6Xn+MZyNrll8MaASomh52SnG8x6WHQ0ASO+G+L629avdspFNE31++HLukpfVNcsDte1Qr0+srVdMFEHLWW4YfGUTMQczLyJRIYQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ckAw1HBt; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ckAw1HBt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E073E1F000E9; Tue, 21 Jul 2026 23:48:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784677687; bh=8C4Am8J8eN/lNe79Ggj9X5yeFTmgWkFhmiw7H77ogsc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=ckAw1HBt9WdOp0zTi2DdVBNsVwukXaDfyRVr2r6FVO6vee2PjLPuS/R49TQhOzl61 4VpwcSEPdxixRK++NTR9OV6b9K/pC1ZByxnVI5O5YEwVvmxF0pbX+LhlzBond/O5kw TJYieUqI278uECci71jL5lbBJe/JgxQGTbcu7xvxjAwB0Wg9H4b7XH+NC9q7gymWtI 1CsbtuvbEGX6C5ADx4lP0EwWTxcarLpxVElQmolWiKAdTf7q+93oJ3jAadoMfms5UO DONp2ZiVUTRzqYpzqh2SqAm9AGaI8dBu3kSujBeVvR3yF4jZLNxE0fN17AFtxeXTAa QtveQEjO8v7dw== Date: Tue, 21 Jul 2026 16:48:02 -0700 From: Nathan Chancellor To: Leandro Ribeiro , Dave Airlie , Thomas Zimmermann , Jocelyn Falempe Cc: dri-devel@lists.freedesktop.org, airlied@gmail.com, daniels@collabora.com, jani.nikula@linux.intel.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, pekka.paalanen@collabora.com, simona@ffwll.ch, ville.syrjala@linux.intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] drm: ensure blend mode supported if pixel format with alpha exposed Message-ID: <20260721234802.GA439272@ax162> References: <20260526181700.25310-1-leandro.ribeiro@collabora.com> <20260526181700.25310-3-leandro.ribeiro@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260526181700.25310-3-leandro.ribeiro@collabora.com> Hi Leandro, + ast folks On Tue, May 26, 2026 at 03:17:00PM -0300, Leandro Ribeiro wrote: > Before "drm/drm_blend: allow blend mode property without PREMULTI", > userspace would have to assume that only PREMULTI was supported by > drivers that didn't expose the blend mode property. But now userspace > shouldn't rely on that, as they can't count with drivers always > supporting PREMULTI. > > Warn if a driver exposes pixel formats with alpha but doesn't expose the > blend mode property. This way userspace doesn't have to guess. Drivers > triggering this warning must be fixed. > > Signed-off-by: Leandro Ribeiro > --- > drivers/gpu/drm/drm_mode_config.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c > index 66f7dc37b597..8cca1dea3b3d 100644 > --- a/drivers/gpu/drm/drm_mode_config.c > +++ b/drivers/gpu/drm/drm_mode_config.c > @@ -674,6 +674,25 @@ static void validate_encoder_possible_crtcs(struct drm_encoder *encoder) > encoder->possible_crtcs, crtc_mask); > } > > +static void validate_blend_mode_for_alpha_formats(struct drm_plane *plane) > +{ > + const struct drm_format_info *fmt; > + u32 i; > + > + /* blend mode property supported, no need to check anything */ > + if (plane->blend_mode_property) > + return; > + > + for (i = 0; i < plane->format_count; i++) { > + fmt = drm_format_info(plane->format_types[i]); > + if (fmt->has_alpha) { > + WARN(1, "[PLANE:%d:%s] pixel format with alpha exposed but " > + "blend mode not setup", plane->base.id, plane->name); I am seeing this warning trigger on a few of my machines in -next. A couple of those use amdgpu, which I see has already been reported in a separate thread. Another one uses ast, which I do not see reported (apologies if I missed it). [ +0.000137] ------------[ cut here ]------------ [ +0.000004] [PLANE:37:plane-1] pixel format with alpha exposed but blend mode not setup [ +0.000019] WARNING: drivers/gpu/drm/drm_mode_config.c:873 at drm_mode_config_validate+0xa24/0xad0, CPU#0: kworker/0:2/507 [ +0.000010] Modules linked in: ghash_ce gf128mul nvme ast(+) nvme_core sbsa_gwdt i2c_algo_bit nvme_keyring nvme_auth xgene_hwmon gpio_dwapb fuse scsi_dh_alua scsi_dh_rdac i2c_dev scsi_dh_emc [ +0.000014] CPU: 0 UID: 0 PID: 507 Comm: kworker/0:2 Not tainted 7.2.0-rc4-next-20260721-00002-g17fa9b81f4c4 #1 PREEMPT(lazy) [ +0.000003] Hardware name: To be filled by O.E.M Ampere Altra Developer Platform/Ampere Altra Developer Platform, BIOS TianoCore 2.10.100.02 (SYS: 2.10.20 [ +0.000002] Workqueue: sync_wq local_pci_probe_callback [ +0.000004] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ +0.000003] pc : drm_mode_config_validate+0xa24/0xad0 [ +0.000002] lr : drm_mode_config_validate+0xa24/0xad0 [ +0.000002] sp : ffff800082df3c30 [ +0.000001] x29: ffff800082df3c60 x28: ffffde7ac3633fc2 x27: 0000000000000001 [ +0.000004] x26: 0000000000000001 x25: 0000000000000002 x24: 0000000000000000 [ +0.000003] x23: ffff07ffb54b0290 x22: ffff07ffb54b0be0 x21: ffffde7ac36ebb13 [ +0.000003] x20: 0000000000000001 x19: ffff07ffb54b0000 x18: ffff800082dd5038 [ +0.000003] x17: 00000000d949c370 x16: 00000000d949c370 x15: ffffde7ac358f156 [ +0.000002] x14: 0000000000000386 x13: ffff081eeebf2850 x12: 0000000000000000 [ +0.000003] x11: 0000000000000000 x10: ffffde7ac44b5850 x9 : 738b2a5f3c615c00 [ +0.000003] x8 : 738b2a5f3c615c00 x7 : 0000000000000000 x6 : 206c65786970205d [ +0.000003] x5 : ffff081f6fcc917b x4 : ffffde7ac36ebb59 x3 : ffffffffffff0a00 [ +0.000002] x2 : 0000000000000001 x1 : 0000000000000000 x0 : 000000000000004b [ +0.000003] Call trace: [ +0.000001] drm_mode_config_validate+0xa24/0xad0 (P) [ +0.000003] drm_dev_register+0x44/0x3d8 [ +0.000004] ast_pci_probe+0x330/0x354 [ast] [ +0.000016] local_pci_probe_callback+0x68/0xc0 [ +0.000002] process_scheduled_works+0x23c/0x668 [ +0.000003] worker_thread+0x218/0x324 [ +0.000003] kthread+0x130/0x180 [ +0.000002] ret_from_fork+0x10/0x20 [ +0.000004] ---[ end trace 0000000000000000 ]--- If there is any other information I can provide or patches I can test, I am more than happy to do so. -- Cheers, Nathan