linux-kernel - [PATCH v2 3/3] drm: Allow simpledrm to setup its emulated FB as firmware provided

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Message-Id: <20220502153900.408522-4-javierm@redhat.com>
Date:   Mon,  2 May 2022 17:39:00 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Javier Martinez Canillas <javierm@...hat.com>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH v2 3/3] drm: Allow simpledrm to setup its emulated FB as firmware provided

Indicate to fbdev subsystem that the registered framebuffer is provided by
the system firmware, so that it can handle accordingly. For example, would
unregister the FB devices if asked to remove the conflicting framebuffers.

Add a new DRM_FB_FW field to drm_fbdev_generic_setup() options parameter.
Drivers can use this to indicate the FB helper initialization that the FB
registered is provided by the firmware, so it can be configured as such.

Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
---

(no changes since v1)

 drivers/gpu/drm/drm_fb_helper.c  |  9 +++++++++
 drivers/gpu/drm/tiny/simpledrm.c |  2 +-
 include/drm/drm_fb_helper.h      | 10 ++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index fd0084ad77c3..775e47c5de1f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1891,6 +1891,10 @@ __drm_fb_helper_initial_config_and_unlock(struct drm_fb_helper *fb_helper,
 		/* don't leak any physical addresses to userspace */
 		info->flags |= FBINFO_HIDE_SMEM_START;
 
+	/* Indicate that the framebuffer is provided by the firmware */
+	if (fb_helper->firmware)
+		info->flags |= FBINFO_MISC_FIRMWARE;
+
 	/* Need to drop locks to avoid recursive deadlock in
 	 * register_framebuffer. This is ok because the only thing left to do is
 	 * register the fbdev emulation instance in kernel_fb_helper_list. */
@@ -2512,6 +2516,8 @@ static const struct drm_client_funcs drm_fbdev_client_funcs = {
  *
  * * DRM_FB_BPP: bits per pixel for the device. If the field is not set,
  *   @dev->mode_config.preferred_depth is used instead.
+ * * DRM_FB_FW: if the framebuffer for the device is provided by the
+ *   system firmware.
  *
  * This function sets up generic fbdev emulation for drivers that supports
  * dumb buffers with a virtual address and that can be mmap'ed.
@@ -2538,6 +2544,7 @@ void drm_fbdev_generic_setup(struct drm_device *dev, unsigned int options)
 {
 	struct drm_fb_helper *fb_helper;
 	unsigned int preferred_bpp = DRM_FB_GET_OPTION(DRM_FB_BPP, options);
+	bool firmware = DRM_FB_GET_OPTION(DRM_FB_FW, options);
 	int ret;
 
 	drm_WARN(dev, !dev->registered, "Device has not been registered.\n");
@@ -2570,6 +2577,8 @@ void drm_fbdev_generic_setup(struct drm_device *dev, unsigned int options)
 		preferred_bpp = 32;
 	fb_helper->preferred_bpp = preferred_bpp;
 
+	fb_helper->firmware = firmware;
+
 	ret = drm_fbdev_client_hotplug(&fb_helper->client);
 	if (ret)
 		drm_dbg_kms(dev, "client hotplug ret=%d\n", ret);
diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index f5b8e864a5cd..5dcc21ea6180 100644
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -901,7 +901,7 @@ static int simpledrm_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	drm_fbdev_generic_setup(dev, 0);
+	drm_fbdev_generic_setup(dev, DRM_FB_SET_OPTION(DRM_FB_FW, 1));
 
 	return 0;
 }
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 740f87560102..77a72d55308d 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -44,6 +44,7 @@ enum mode_set_atomic {
 };
 
 #define DRM_FB_BPP_MASK GENMASK(7, 0)
+#define DRM_FB_FW_MASK GENMASK(8, 8)
 
 /* Using the GNU statement expression extension */
 #define DRM_FB_OPTION(option, value)				\
@@ -197,6 +198,15 @@ struct drm_fb_helper {
 	 * See also: @deferred_setup
 	 */
 	int preferred_bpp;
+
+	/**
+	 * @firmware:
+	 *
+	 * Set if the driver indicates to the FB helper initialization that the
+	 * framebuffer for the device being registered is provided by firmware,
+	 * so that it can pass this on when registering the framebuffer device.
+	 */
+	bool firmware;
 };
 
 static inline struct drm_fb_helper *
-- 
2.35.1