From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-op-o10.zoho.com (sender4-op-o10.zoho.com [136.143.188.10]) (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 D9F3335F18A for ; Mon, 25 May 2026 23:38:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.10 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779752317; cv=pass; b=TVTC4zrFKYDFshrZG1S9OmmFfaXpb6nQikc1m91ulYW3326dmB7wb4+c8asdMr60vk2s/dwCmHaK19EfW0vUh33W3k5WzQK/e6ilIOFVx2Sw+8zrwI3UCQrGgqEdLKkrqo7XoQQEQCNPKnDauaRKYsBDJTJ5xtr46O0rCGa8k0o= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779752317; c=relaxed/simple; bh=kk/0b2IEHR1gMZ+VXyUXLlWJIvEmRhVRcRXggBPJyC4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Pxsn0z02oZwhBy5EF+vCp1r8z+7EJCHgXePriSWZ+JyIpHk/DOFnyAlne8HlX017y6E2n3l5B6bsYtOsLcaysHtt6/eYRVPLs8vRhW+3STPy23appYJGXY8xWZIxJGoc2Smflc0NIcf0a0UhJ9F2+5TIDZXftra5RgKH/mrTPa4= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=leandro.ribeiro@collabora.com header.b=R4i0IHMa; arc=pass smtp.client-ip=136.143.188.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=leandro.ribeiro@collabora.com header.b="R4i0IHMa" ARC-Seal: i=1; a=rsa-sha256; t=1779752306; cv=none; d=zohomail.com; s=zohoarc; b=Osc1iJdh9i//7IziDWI8TRqMtUIiNR5OuD2WNgr1FPdTgEx0i2U0OujaW0GCI+3bVvFwbg/eGPDxEmjFQKX7FbzWyNyvxdy0gWKriEKGNHGqQPPQJNnjvw9FJ2q/7oQisq1vmTnp8i2EasSRKrz+cqfCeo31pHCGcMUSRfvxqLo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1779752306; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=AWzAifp2Eq9PNUKyhqA9ZAbFibzkc5QldnOyWDzTtdY=; b=QbPmZc/xUwgXkE07vfweI6zfHUzODSZ1QdEK1ACJUUKEhjolrTxdhNLpEtyCQ88x9DvsYK0bDStd/v+Rrub3yPIcmfpotzBm2m4Eo9kOt9kTGPmzeGbsTNUeSLLze6XizH5FKXbzP83mabOhK4+AjW7KNwBss8rf0gEe1Lps7CY= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=leandro.ribeiro@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1779752306; s=zohomail; d=collabora.com; i=leandro.ribeiro@collabora.com; h=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:Cc:Cc:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=AWzAifp2Eq9PNUKyhqA9ZAbFibzkc5QldnOyWDzTtdY=; b=R4i0IHMaoCc3dMqg3h5An09/RCpaMWWuHCDvLkUegDYAAkLCfiOPg34IPD8UGOdp o0JrC6lBcoi4wuM8ByibaVA/TN65O/O6uNElBxWmxz3HMmpLasEqN5MkPNMCB1sEYrJ C5hVincZMLX5/IEI10PGyPltgiYg2HLoKY9MiKVc= Received: by mx.zohomail.com with SMTPS id 1779752303243559.4926896587914; Mon, 25 May 2026 16:38:23 -0700 (PDT) Message-ID: <020b2afd-b056-4502-9ad5-51eabba94074@collabora.com> Date: Mon, 25 May 2026 20:38:16 -0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] drm: ensure blend mode supported if alpha exposed To: =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= 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, tzimmermann@suse.de, linux-kernel@vger.kernel.org References: <20260518175429.80615-1-leandro.ribeiro@collabora.com> <20260518175429.80615-3-leandro.ribeiro@collabora.com> Content-Language: en-US From: Leandro Ribeiro In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ZohoMailClient: External On 5/22/26 3:24 PM, Ville Syrjälä wrote: > On Mon, May 18, 2026 at 02:54:29PM -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 relly on that, as they can't count with drivers always >> supporting PREMULTI. >> >> Error out if a driver expose alpha property or pixel formats with alpha >> and does not expose the blend mode property. This way userspace don't >> have to guess. Drivers that hit such error must be fixed. >> >> Signed-off-by: Leandro Ribeiro >> --- >> drivers/gpu/drm/drm_crtc_internal.h | 2 +- >> drivers/gpu/drm/drm_drv.c | 7 ++++-- >> drivers/gpu/drm/drm_mode_config.c | 37 +++++++++++++++++++++++++++-- >> 3 files changed, 41 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h >> index c09409229644..2a4862202496 100644 >> --- a/drivers/gpu/drm/drm_crtc_internal.h >> +++ b/drivers/gpu/drm/drm_crtc_internal.h >> @@ -95,7 +95,7 @@ int drm_mode_setcrtc(struct drm_device *dev, >> /* drm_mode_config.c */ >> int drm_modeset_register_all(struct drm_device *dev); >> void drm_modeset_unregister_all(struct drm_device *dev); >> -void drm_mode_config_validate(struct drm_device *dev); >> +int drm_mode_config_validate(struct drm_device *dev); >> >> /* drm_modes.c */ >> const char *drm_get_mode_status_name(enum drm_mode_status status); >> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c >> index 985c283cf59f..def78046a963 100644 >> --- a/drivers/gpu/drm/drm_drv.c >> +++ b/drivers/gpu/drm/drm_drv.c >> @@ -1059,8 +1059,11 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags) >> const struct drm_driver *driver = dev->driver; >> int ret; >> >> - if (!driver->load) >> - drm_mode_config_validate(dev); >> + if (!driver->load) { >> + ret = drm_mode_config_validate(dev); >> + if (ret) >> + return ret; >> + } >> >> WARN_ON(!dev->managed.final_kfree); >> >> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c >> index 66f7dc37b597..18c6b5707532 100644 >> --- a/drivers/gpu/drm/drm_mode_config.c >> +++ b/drivers/gpu/drm/drm_mode_config.c >> @@ -674,16 +674,45 @@ static void validate_encoder_possible_crtcs(struct drm_encoder *encoder) >> encoder->possible_crtcs, crtc_mask); >> } >> >> -void drm_mode_config_validate(struct drm_device *dev) >> +static int plane_alpha_require_blend_mode(struct drm_plane *plane) >> +{ >> + struct drm_device *dev = plane->dev; >> + const struct drm_format_info *fmt; >> + u32 i; >> + >> + /* blend mode property supported, no need to check anything */ >> + if (plane->blend_mode_property) >> + return 0; >> + >> + if (plane->alpha_property) { >> + drm_err(dev, "[PLANE:%d:%s] alpha property exposed but blend mode not setup", >> + plane->base.id, plane->name); >> + return -EINVAL; >> + } > > Why this? I don't think the constant alpha property has anything > really to do with the per-pixel alpha stuff. You’re right: if the pixel format has no alpha channel, the constant alpha property produces identical results for COVERAGE and PREMULTI. > >> + >> + for (i = 0; i < plane->format_count; i++) { >> + fmt = drm_format_info(plane->format_types[i]); >> + if (fmt->has_alpha) { >> + drm_err(dev, "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup", >> + plane->base.id, plane->name); >> + return -EINVAL; >> + } >> + } >> + >> + return 0; >> +} >> + >> +int drm_mode_config_validate(struct drm_device *dev) >> { >> struct drm_encoder *encoder; >> struct drm_crtc *crtc; >> struct drm_plane *plane; >> u32 primary_with_crtc = 0, cursor_with_crtc = 0; >> unsigned int num_primary = 0; >> + int ret = 0; >> >> if (!drm_core_check_feature(dev, DRIVER_MODESET)) >> - return; >> + return ret; >> >> drm_for_each_encoder(encoder, dev) >> fixup_encoder_possible_clones(encoder); >> @@ -732,9 +761,13 @@ void drm_mode_config_validate(struct drm_device *dev) >> drm_for_each_plane(plane, dev) { >> if (plane->type == DRM_PLANE_TYPE_PRIMARY) >> num_primary++; >> + >> + ret |= plane_alpha_require_blend_mode(plane); >> } >> >> WARN(num_primary != dev->mode_config.num_crtc, >> "Must have as many primary planes as there are CRTCs, but have %u primary planes and %u CRTCs", >> num_primary, dev->mode_config.num_crtc); >> + >> + return ret; >> } >> -- >> 2.54.0 > -- Leandro Ribeiro