From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5AEEDC6FD1D for ; Fri, 17 Mar 2023 13:14:00 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0CB3410E387; Fri, 17 Mar 2023 13:13:54 +0000 (UTC) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by gabe.freedesktop.org (Postfix) with ESMTPS id B831C10E27A; Fri, 17 Mar 2023 13:13:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1679058831; x=1710594831; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=wuG9YPAI9Dr1JFK620ho0x3CCrqr8SYUVL76KTvgJ0s=; b=bNCScKG2N8GASqW0i9Vl6WIQOPauFx9SEAZQ12+YSostgUJ7mJX5qGM8 K+JP2Uqa+3mDHCzMzuRHWxJ0mzQeUySfTDhMWCERxF5eGASJ9DTSA6HlN Vfw1EfIvah5AoRNyURvLDUtBSjyJoCmhC1DkjutuhMEQ/T0JcF/QHYm8p EWUf2Uc0vTPIuOaFUffhiIiBdF+oN3ZiSAM/jtUbNhoMagY3m53gvQZSk VT1p2Kb1vYMPLdY5FFlMQ4814X2q6ryVkk1acsp3FXpLMW6pitg/ZlhcS z3oCu25Kzpyc/IQzTBAbfOfzakT7jZIE/42oO7KgAZF0c25hotAU4OX+L w==; X-IronPort-AV: E=McAfee;i="6600,9927,10652"; a="340616587" X-IronPort-AV: E=Sophos;i="5.98,268,1673942400"; d="scan'208";a="340616587" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2023 06:13:51 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10652"; a="630282153" X-IronPort-AV: E=Sophos;i="5.98,268,1673942400"; d="scan'208";a="630282153" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.70]) by orsmga003.jf.intel.com with SMTP; 17 Mar 2023 06:13:48 -0700 Received: by stinkbox (sSMTP sendmail emulation); Fri, 17 Mar 2023 15:13:47 +0200 Date: Fri, 17 Mar 2023 15:13:47 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jonas =?iso-8859-1?Q?=C5dahl?= Message-ID: References: <20230208211016.7034-1-ville.syrjala@linux.intel.com> <20230313163311.11379-1-ville.syrjala@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Patchwork-Hint: comment Subject: Re: [Intel-gfx] [PATCH v3 1/2] drm: Introduce plane SIZE_HINTS property X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, Pekka Paalanen , Jonas =?iso-8859-1?Q?=C5dahl?= , dri-devel@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Fri, Mar 17, 2023 at 01:21:40PM +0100, Jonas Ådahl wrote: > On Fri, Mar 17, 2023 at 01:33:25PM +0200, Ville Syrjälä wrote: > > On Fri, Mar 17, 2023 at 11:34:16AM +0100, Jonas Ådahl wrote: > > > On Mon, Mar 13, 2023 at 06:33:11PM +0200, Ville Syrjala wrote: > > > > From: Ville Syrjälä > > > > > > > > Add a new immutable plane property by which a plane can advertise > > > > a handful of recommended plane sizes. This would be mostly exposed > > > > by cursor planes as a slightly more capable replacement for > > > > the DRM_CAP_CURSOR_WIDTH/HEIGHT caps, which can only declare > > > > a one size fits all limit for the whole device. > > > > > > > > Currently eg. amdgpu/i915/nouveau just advertize the max cursor > > > > size via the cursor size caps. But always using the max sized > > > > cursor can waste a surprising amount of power, so a better > > > > stragey is desirable. > > > > > > > > Most other drivers don't specify any cursor size at all, in > > > > which case the ioctl code just claims that 64x64 is a great > > > > choice. Whether that is actually true is debatable. > > > > > > > > A poll of various compositor developers informs us that > > > > blindly probing with setcursor/atomic ioctl to determine > > > > suitable cursor sizes is not acceptable, thus the > > > > introduction of the new property to supplant the cursor > > > > size caps. The compositor will now be free to select a > > > > more optimal cursor size from the short list of options. > > > > > > > > Note that the reported sizes (either via the property or the > > > > caps) make no claims about things such as plane scaling. So > > > > these things should only really be consulted for simple > > > > "cursor like" use cases. > > > > > > > > v2: Try to add some docs > > > > v3: Specify that value 0 is reserved for future use (basic idea from Jonas) > > > > Drop the note about typical hardware (Pekka) > > > > > > > > Cc: Simon Ser > > > > Cc: Jonas Ådahl > > > > Cc: Daniel Stone > > > > Cc: Pekka Paalanen > > > > Acked-by: Harry Wentland > > > > Acked-by: Pekka Paalanen > > > > Signed-off-by: Ville Syrjälä > > > > --- > > > > drivers/gpu/drm/drm_mode_config.c | 7 ++++ > > > > drivers/gpu/drm/drm_plane.c | 53 +++++++++++++++++++++++++++++++ > > > > include/drm/drm_mode_config.h | 5 +++ > > > > include/drm/drm_plane.h | 4 +++ > > > > include/uapi/drm/drm_mode.h | 11 +++++++ > > > > 5 files changed, 80 insertions(+) > > > > > > > > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c > > > > index 87eb591fe9b5..21860f94a18c 100644 > > > > --- a/drivers/gpu/drm/drm_mode_config.c > > > > +++ b/drivers/gpu/drm/drm_mode_config.c > > > > @@ -374,6 +374,13 @@ static int drm_mode_create_standard_properties(struct drm_device *dev) > > > > return -ENOMEM; > > > > dev->mode_config.modifiers_property = prop; > > > > > > > > + prop = drm_property_create(dev, > > > > + DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_BLOB, > > > > + "SIZE_HINTS", 0); > > > > + if (!prop) > > > > + return -ENOMEM; > > > > + dev->mode_config.size_hints_property = prop; > > > > + > > > > return 0; > > > > } > > > > > > > > diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c > > > > index 24e7998d1731..d2a6fdff1a57 100644 > > > > --- a/drivers/gpu/drm/drm_plane.c > > > > +++ b/drivers/gpu/drm/drm_plane.c > > > > @@ -140,6 +140,26 @@ > > > > * DRM_FORMAT_MOD_LINEAR. Before linux kernel release v5.1 there have been > > > > * various bugs in this area with inconsistencies between the capability > > > > * flag and per-plane properties. > > > > + * > > > > + * SIZE_HINTS: > > > > + * Blob property which contains the set of recommended plane size > > > > + * which can used for simple "cursor like" use cases (eg. no scaling). > > > > + * Using these hints frees userspace from extensive probing of > > > > + * supported plane sizes through atomic/setcursor ioctls. > > > > + * > > > > + * For optimal usage userspace should pick the smallest size > > > > + * that satisfies its own requirements. > > > > + * > > > > + * The blob contains an array of struct drm_plane_size_hint. > > > > + * > > > > + * Drivers should only attach this property to planes that > > > > + * support a very limited set of sizes. > > > > + * > > > > + * Note that property value 0 (ie. no blob) is reserved for potential > > > > + * future use. Current userspace is expected to ignore the property > > > > + * if the value is 0, and fall back to some other means (eg. > > > > + * &DRM_CAP_CURSOR_WIDTH and &DRM_CAP_CURSOR_HEIGHT) to determine > > > > + * the appropriate plane size to use. > > > > > > Does this intend to mean userspace has the kernel's blessing on choosing > > > an arbitrary size as long as it's smaller than &DRM_CAP_CURSOR_WIDTH x > > > &DRM_CAP_CURSOR_HEIGHT? > > > > > > It's a bit to vague for me to make a confident interpretation whether I > > > can, or whether I should pretend I didn't see SIZE_HINTS and apply the > > > old logic, meaning only using the exact cap size. > > > > Using the exact cap size is the only thing more or less > > guaranteed to work. But other approaches (such as probing > > the size with atomic/cursor ioctls) can also be used. > > I think you should then just disallow drivers for exposing SIZE_HINTS > with the value 0, and make it a bug if they do, to let userspace know > when the value 0 means anything. Now I'm very confused. Previously you asked to have a special value reserved for the case where the driver+hw can use any size below the cap declated max. That is why I declared this blob=0 as a reserved value for the future. But now you say you don't want that anymore? > > In other words, userspace should *not* ignore the property value being > 0, but treat it as a kernel bug if there is a SIZE_HINTS only containing > a 0, until the value 0 has gotten any meaning. Otherwise I don't see how > it'll be usable in the future, since userspace doesn't know the > difference between 'legacy 0' and 'new 0' once it's defined to mean > anything. > > > Jonas -- Ville Syrjälä Intel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9ADAAC74A5B for ; Fri, 17 Mar 2023 13:13:54 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7B98C10E27A; Fri, 17 Mar 2023 13:13:53 +0000 (UTC) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by gabe.freedesktop.org (Postfix) with ESMTPS id B831C10E27A; Fri, 17 Mar 2023 13:13:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1679058831; x=1710594831; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=wuG9YPAI9Dr1JFK620ho0x3CCrqr8SYUVL76KTvgJ0s=; b=bNCScKG2N8GASqW0i9Vl6WIQOPauFx9SEAZQ12+YSostgUJ7mJX5qGM8 K+JP2Uqa+3mDHCzMzuRHWxJ0mzQeUySfTDhMWCERxF5eGASJ9DTSA6HlN Vfw1EfIvah5AoRNyURvLDUtBSjyJoCmhC1DkjutuhMEQ/T0JcF/QHYm8p EWUf2Uc0vTPIuOaFUffhiIiBdF+oN3ZiSAM/jtUbNhoMagY3m53gvQZSk VT1p2Kb1vYMPLdY5FFlMQ4814X2q6ryVkk1acsp3FXpLMW6pitg/ZlhcS z3oCu25Kzpyc/IQzTBAbfOfzakT7jZIE/42oO7KgAZF0c25hotAU4OX+L w==; X-IronPort-AV: E=McAfee;i="6600,9927,10652"; a="340616587" X-IronPort-AV: E=Sophos;i="5.98,268,1673942400"; d="scan'208";a="340616587" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2023 06:13:51 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10652"; a="630282153" X-IronPort-AV: E=Sophos;i="5.98,268,1673942400"; d="scan'208";a="630282153" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.70]) by orsmga003.jf.intel.com with SMTP; 17 Mar 2023 06:13:48 -0700 Received: by stinkbox (sSMTP sendmail emulation); Fri, 17 Mar 2023 15:13:47 +0200 Date: Fri, 17 Mar 2023 15:13:47 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jonas =?iso-8859-1?Q?=C5dahl?= Subject: Re: [PATCH v3 1/2] drm: Introduce plane SIZE_HINTS property Message-ID: References: <20230208211016.7034-1-ville.syrjala@linux.intel.com> <20230313163311.11379-1-ville.syrjala@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Patchwork-Hint: comment X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, Pekka Paalanen , Jonas =?iso-8859-1?Q?=C5dahl?= , dri-devel@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Fri, Mar 17, 2023 at 01:21:40PM +0100, Jonas Ådahl wrote: > On Fri, Mar 17, 2023 at 01:33:25PM +0200, Ville Syrjälä wrote: > > On Fri, Mar 17, 2023 at 11:34:16AM +0100, Jonas Ådahl wrote: > > > On Mon, Mar 13, 2023 at 06:33:11PM +0200, Ville Syrjala wrote: > > > > From: Ville Syrjälä > > > > > > > > Add a new immutable plane property by which a plane can advertise > > > > a handful of recommended plane sizes. This would be mostly exposed > > > > by cursor planes as a slightly more capable replacement for > > > > the DRM_CAP_CURSOR_WIDTH/HEIGHT caps, which can only declare > > > > a one size fits all limit for the whole device. > > > > > > > > Currently eg. amdgpu/i915/nouveau just advertize the max cursor > > > > size via the cursor size caps. But always using the max sized > > > > cursor can waste a surprising amount of power, so a better > > > > stragey is desirable. > > > > > > > > Most other drivers don't specify any cursor size at all, in > > > > which case the ioctl code just claims that 64x64 is a great > > > > choice. Whether that is actually true is debatable. > > > > > > > > A poll of various compositor developers informs us that > > > > blindly probing with setcursor/atomic ioctl to determine > > > > suitable cursor sizes is not acceptable, thus the > > > > introduction of the new property to supplant the cursor > > > > size caps. The compositor will now be free to select a > > > > more optimal cursor size from the short list of options. > > > > > > > > Note that the reported sizes (either via the property or the > > > > caps) make no claims about things such as plane scaling. So > > > > these things should only really be consulted for simple > > > > "cursor like" use cases. > > > > > > > > v2: Try to add some docs > > > > v3: Specify that value 0 is reserved for future use (basic idea from Jonas) > > > > Drop the note about typical hardware (Pekka) > > > > > > > > Cc: Simon Ser > > > > Cc: Jonas Ådahl > > > > Cc: Daniel Stone > > > > Cc: Pekka Paalanen > > > > Acked-by: Harry Wentland > > > > Acked-by: Pekka Paalanen > > > > Signed-off-by: Ville Syrjälä > > > > --- > > > > drivers/gpu/drm/drm_mode_config.c | 7 ++++ > > > > drivers/gpu/drm/drm_plane.c | 53 +++++++++++++++++++++++++++++++ > > > > include/drm/drm_mode_config.h | 5 +++ > > > > include/drm/drm_plane.h | 4 +++ > > > > include/uapi/drm/drm_mode.h | 11 +++++++ > > > > 5 files changed, 80 insertions(+) > > > > > > > > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c > > > > index 87eb591fe9b5..21860f94a18c 100644 > > > > --- a/drivers/gpu/drm/drm_mode_config.c > > > > +++ b/drivers/gpu/drm/drm_mode_config.c > > > > @@ -374,6 +374,13 @@ static int drm_mode_create_standard_properties(struct drm_device *dev) > > > > return -ENOMEM; > > > > dev->mode_config.modifiers_property = prop; > > > > > > > > + prop = drm_property_create(dev, > > > > + DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_BLOB, > > > > + "SIZE_HINTS", 0); > > > > + if (!prop) > > > > + return -ENOMEM; > > > > + dev->mode_config.size_hints_property = prop; > > > > + > > > > return 0; > > > > } > > > > > > > > diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c > > > > index 24e7998d1731..d2a6fdff1a57 100644 > > > > --- a/drivers/gpu/drm/drm_plane.c > > > > +++ b/drivers/gpu/drm/drm_plane.c > > > > @@ -140,6 +140,26 @@ > > > > * DRM_FORMAT_MOD_LINEAR. Before linux kernel release v5.1 there have been > > > > * various bugs in this area with inconsistencies between the capability > > > > * flag and per-plane properties. > > > > + * > > > > + * SIZE_HINTS: > > > > + * Blob property which contains the set of recommended plane size > > > > + * which can used for simple "cursor like" use cases (eg. no scaling). > > > > + * Using these hints frees userspace from extensive probing of > > > > + * supported plane sizes through atomic/setcursor ioctls. > > > > + * > > > > + * For optimal usage userspace should pick the smallest size > > > > + * that satisfies its own requirements. > > > > + * > > > > + * The blob contains an array of struct drm_plane_size_hint. > > > > + * > > > > + * Drivers should only attach this property to planes that > > > > + * support a very limited set of sizes. > > > > + * > > > > + * Note that property value 0 (ie. no blob) is reserved for potential > > > > + * future use. Current userspace is expected to ignore the property > > > > + * if the value is 0, and fall back to some other means (eg. > > > > + * &DRM_CAP_CURSOR_WIDTH and &DRM_CAP_CURSOR_HEIGHT) to determine > > > > + * the appropriate plane size to use. > > > > > > Does this intend to mean userspace has the kernel's blessing on choosing > > > an arbitrary size as long as it's smaller than &DRM_CAP_CURSOR_WIDTH x > > > &DRM_CAP_CURSOR_HEIGHT? > > > > > > It's a bit to vague for me to make a confident interpretation whether I > > > can, or whether I should pretend I didn't see SIZE_HINTS and apply the > > > old logic, meaning only using the exact cap size. > > > > Using the exact cap size is the only thing more or less > > guaranteed to work. But other approaches (such as probing > > the size with atomic/cursor ioctls) can also be used. > > I think you should then just disallow drivers for exposing SIZE_HINTS > with the value 0, and make it a bug if they do, to let userspace know > when the value 0 means anything. Now I'm very confused. Previously you asked to have a special value reserved for the case where the driver+hw can use any size below the cap declated max. That is why I declared this blob=0 as a reserved value for the future. But now you say you don't want that anymore? > > In other words, userspace should *not* ignore the property value being > 0, but treat it as a kernel bug if there is a SIZE_HINTS only containing > a 0, until the value 0 has gotten any meaning. Otherwise I don't see how > it'll be usable in the future, since userspace doesn't know the > difference between 'legacy 0' and 'new 0' once it's defined to mean > anything. > > > Jonas -- Ville Syrjälä Intel