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Fri, 27 Mar 2026 07:21:49 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id tVUpMw0wxmkQHAAAD6G6ig (envelope-from ); Fri, 27 Mar 2026 07:21:49 +0000 Message-ID: <243dbc45-cb11-4dfe-b8d1-e08f1b5f73b6@suse.de> Date: Fri, 27 Mar 2026 08:21:49 +0100 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 1/3] drm: Introduce DRM_MODE_DUMB_KERNEL_MAP flag To: Chen-Yu Tsai , Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter Cc: Rob Herring , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20260326100248.1171828-1-wenst@chromium.org> <20260326100248.1171828-2-wenst@chromium.org> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <20260326100248.1171828-2-wenst@chromium.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Score: -4.30 X-Spam-Level: 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]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; FREEMAIL_TO(0.00)[chromium.org,linux.intel.com,kernel.org,gmail.com,ffwll.ch]; RCPT_COUNT_SEVEN(0.00)[9]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; URIBL_BLOCKED(0.00)[suse.com:url,suse.de:mid,chromium.org:email,imap1.dmz-prg2.suse.org:helo]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.com:url,imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO Hi Am 26.03.26 um 11:01 schrieb Chen-Yu Tsai: > From: Rob Herring > > Introduce a new flag, DRM_MODE_DUMB_KERNEL_MAP, for struct > drm_mode_create_dumb. This flag is for internal kernel use to indicate > if dumb buffer allocation needs a kernel mapping. This is needed only for > GEM DMA where creating a kernel mapping or not has to be decided at > allocation time because creating a mapping on demand (with vmap()) is not > guaranteed to work. I still don't understand what you're trying to achieve. As I pointed out, ever driver's memory manager potentially requires a vmap. Passing around flags will not solve that problem. If vmap is not possible, the driver should not provide the vmap callbacks in the first place. Best regards Thomas > > Several drivers are using reimplementing the GEM DMA helpers because > they distinguish between kernel and userspace allocations to create a > kernel mapping or not. Adding a flag allows migrating these drivers > to the helpers while preserving their existing behavior. These include > exynos, rockchip, and previously mediatek. > > Update the callers of drm_mode_dumb_create() to set > drm_mode_dumb_create.flags to appropriate defaults. Currently, flags can > be set to anything by userspace, but is unused within the kernel. Let's > force flags to zero (no kernel mapping) for userspace callers by default. > For in kernel clients, set DRM_MODE_DUMB_KERNEL_MAP by default. Drivers > can override this as needed. > > Signed-off-by: Rob Herring > [wenst@chromium.org: Emit warning (once) if args->flags is not zero] > [wenst@chromium.org: Moved flag def. to include/drm/drm_dumb_buffers.h] > Signed-off-by: Chen-Yu Tsai > --- > Changes since v2: > - Switched to drm_warn_once() > - Moved flag definition from include/uapi/ to include/drm/drm_dumb_buffers.h > - Reworded commit message > > Changes since v1: > - Emit warning if args->flags is not zero > --- > drivers/gpu/drm/drm_client.c | 2 ++ > drivers/gpu/drm/drm_dumb_buffers.c | 4 ++++ > include/drm/drm_dumb_buffers.h | 3 +++ > 3 files changed, 9 insertions(+) > > diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c > index 46c465bce98c..3d3e61823cc1 100644 > --- a/drivers/gpu/drm/drm_client.c > +++ b/drivers/gpu/drm/drm_client.c > @@ -14,6 +14,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -404,6 +405,7 @@ drm_client_buffer_create_dumb(struct drm_client_dev *client, u32 width, u32 heig > dumb_args.width = width; > dumb_args.height = height; > dumb_args.bpp = drm_format_info_bpp(info, 0); > + dumb_args.flags = DRM_MODE_DUMB_KERNEL_MAP; > ret = drm_mode_create_dumb(dev, &dumb_args, client->file); > if (ret) > return ERR_PTR(ret); > diff --git a/drivers/gpu/drm/drm_dumb_buffers.c b/drivers/gpu/drm/drm_dumb_buffers.c > index e2b62e5fb891..60f4c2d08641 100644 > --- a/drivers/gpu/drm/drm_dumb_buffers.c > +++ b/drivers/gpu/drm/drm_dumb_buffers.c > @@ -233,6 +233,10 @@ int drm_mode_create_dumb_ioctl(struct drm_device *dev, > struct drm_mode_create_dumb *args = data; > int err; > > + if (args->flags) > + drm_warn_once(dev, "drm_mode_create_dumb.flags is not zero.\n"); > + args->flags = 0; > + > err = drm_mode_create_dumb(dev, args, file_priv); > if (err) { > args->handle = 0; > diff --git a/include/drm/drm_dumb_buffers.h b/include/drm/drm_dumb_buffers.h > index 1f3a8236fb3d..4657e44533f4 100644 > --- a/include/drm/drm_dumb_buffers.h > +++ b/include/drm/drm_dumb_buffers.h > @@ -6,6 +6,9 @@ > struct drm_device; > struct drm_mode_create_dumb; > > +/* drm_mode_create_dumb flags for internal use */ > +#define DRM_MODE_DUMB_KERNEL_MAP (1<<0) > + > int drm_mode_size_dumb(struct drm_device *dev, > struct drm_mode_create_dumb *args, > unsigned long hw_pitch_align, -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)