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Tue, 17 Mar 2026 08:12:33 +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 e0YjKfEMuWlBVwAAD6G6ig (envelope-from ); Tue, 17 Mar 2026 08:12:33 +0000 Message-ID: <607daaca-79ed-45b2-941e-1680a17618e8@suse.de> Date: Tue, 17 Mar 2026 09:12:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] drm: Introduce DRM_MODE_DUMB_KERNEL_MAP flag To: Chen-Yu Tsai , Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter Cc: Rob Herring , Laurent Pinchart , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, asahi@lists.linux.dev References: <20260317064049.696795-1-wenst@chromium.org> <20260317064049.696795-3-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: <20260317064049.696795-3-wenst@chromium.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FREEMAIL_TO(0.00)[chromium.org,linux.intel.com,kernel.org,gmail.com,ffwll.ch]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FUZZY_RATELIMITED(0.00)[rspamd.com]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; MID_RHS_MATCH_FROM(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCPT_COUNT_SEVEN(0.00)[11]; ASN(0.00)[asn:32098, ipnet:2800::/6, country:US]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.com:url,suse.de:dkim,suse.de:mid] X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Queue-Id: 119DA5BCFD X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260317_011238_118747_B83D6DDB X-CRM114-Status: GOOD ( 29.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Am 17.03.26 um 07:40 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 > CMA 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. Several drivers are using CMA, but not the CMA helpers because > they distinguish between kernel and userspace allocations to create a > kernel mapping or not. Any dumb allocation might require vmap. This is not limited to internal buffers.  Because if the dumb buffer is shared with another driver, that driver might require the vmap for displaying the buffer content. There are enough of such drivers. > > 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 if args->flags is not zero] > Signed-off-by: Chen-Yu Tsai > --- > Changes since v1: > - Emit warning if args->flags is not zero > --- > drivers/gpu/drm/drm_client.c | 1 + > drivers/gpu/drm/drm_dumb_buffers.c | 4 ++++ > include/uapi/drm/drm_mode.h | 2 ++ > 3 files changed, 7 insertions(+) > > diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c > index 46c465bce98c..1a57e7eadc0f 100644 > --- a/drivers/gpu/drm/drm_client.c > +++ b/drivers/gpu/drm/drm_client.c > @@ -404,6 +404,7 @@ 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..ccdcc401d4dc 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(dev, "drm_mode_create_dumb.flags is not zero.\n"); At most use drm_warn_once() to not let this spam the kernel log. > + args->flags = 0; > + > err = drm_mode_create_dumb(dev, args, file_priv); > if (err) { > args->handle = 0; > diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h > index 3693d82b5279..7d5f50e4af70 100644 > --- a/include/uapi/drm/drm_mode.h > +++ b/include/uapi/drm/drm_mode.h > @@ -1272,6 +1272,8 @@ struct drm_mode_create_dumb { > __u64 size; > }; > > +#define DRM_MODE_DUMB_KERNEL_MAP (1<<0) /* For internal kernel use */ > + If this is an internal flag, it should not live in the UAPI header. include/drm/drm_dumb_buffers.h would be a good place. Best regards Thomas > /* set up for mmap of a dumb scanout buffer */ > struct drm_mode_map_dumb { > /** Handle for the object being mapped. */ -- -- 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)