[RFC 1/6] RFC: drm: add support for tiled/compressed/etc modifier in addfb2

Tvrtko Ursulin
2015-01-30T17:37:22Z

From: Rob Clark <robdclark@gmail.com>

In DRM/KMS we are lacking a good way to deal with tiled/compressed
formats. Especially in the case of dmabuf/prime buffer sharing, where
we cannot always rely on under-the-hood flags passed to driver specific
gem-create ioctl to pass around these extra flags.

The proposal is to add a per-plane format modifier. This allows to, if
necessary, use different tiling patters for sub-sampled planes, etc.
The format modifiers are added at the end of the ioctl struct, so for
legacy userspace it will be zero padded.

v1: original
v1.5: increase modifier to 64b

v2: Incorporate review comments from the big thread, plus a few more.

- Add a getcap so that userspace doesn't have to jump through hoops.
- Allow modifiers only when a flag is set. That way drivers know when
they're dealing with old userspace and need to fish out e.g. tiling
from other information.
- After rolling out checks for ->modifier to all drivers I've decided
that this is way too fragile and needs an explicit opt-in flag. So
do that instead.
- Add a define (just for documentation really) for the "NONE"
modifier. Imo we don't need to add mask #defines since drivers
really should only do exact matches against values defined with
fourcc_mod_code.
- Drop the Samsung tiling modifier on Rob's request since he's not yet
sure whether that one is accurate.

v3:
- Also add a new ->modifier[] array to struct drm_framebuffer and fill
it in drm_helper_mode_fill_fb_struct. Requested by Tvrtko Uruslin.
- Remove TODO in comment and add code comment that modifiers should be
properly documented, requested by Rob.

v4: Balance parens, spotted by Tvrtko.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Stone <daniel@fooishbar.org>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Michel Dänzer <michel@daenzer.net>
Signed-off-by: Rob Clark <robdclark@gmail.com> (v1.5)
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
drivers/gpu/drm/drm_crtc.c | 14 +++++++++++++-
drivers/gpu/drm/drm_crtc_helper.c | 1 +
drivers/gpu/drm/drm_ioctl.c | 3 +++
include/drm/drm_crtc.h | 4 ++++
include/uapi/drm/drm.h | 1 +
include/uapi/drm/drm_fourcc.h | 32 ++++++++++++++++++++++++++++++++
include/uapi/drm/drm_mode.h | 9 +++++++++
7 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 6b00173..e6e2de3 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -3261,6 +3261,12 @@ static int framebuffer_check(const struct drm_mode_fb_cmd2 *r)
DRM_DEBUG_KMS("bad pitch %u for plane %d\n", r->pitches[i], i);
return -EINVAL;
}
+
+ if (r->modifier[i] && !(r->flags & DRM_MODE_FB_MODIFIERS)) {
+ DRM_DEBUG_KMS("bad fb modifier %llu for plane %d\n",
+ r->modifier[i], i);
+ return -EINVAL;
+ }
}

return 0;
@@ -3274,7 +3280,7 @@ static struct drm_framebuffer *add_framebuffer_internal(struct drm_device *dev,
struct drm_framebuffer *fb;
int ret;

- if (r->flags & ~DRM_MODE_FB_INTERLACED) {
+ if (r->flags & ~(DRM_MODE_FB_INTERLACED | DRM_MODE_FB_MODIFIERS)) {
DRM_DEBUG_KMS("bad framebuffer flags 0x%08x\n", r->flags);
return ERR_PTR(-EINVAL);
}
@@ -3290,6 +3296,12 @@ static struct drm_framebuffer *add_framebuffer_internal(struct drm_device *dev,
return ERR_PTR(-EINVAL);
}

+ if (r->flags & DRM_MODE_FB_MODIFIERS &&
+ !dev->mode_config.allow_fb_modifiers) {
+ DRM_DEBUG_KMS("driver does not support fb modifiers\n");
+ return ERR_PTR(-EINVAL);
+ }
+
ret = framebuffer_check(r);
if (ret)
return ERR_PTR(ret);
diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index b1979e7..3053aab 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -837,6 +837,7 @@ void drm_helper_mode_fill_fb_struct(struct drm_framebuffer *fb,
for (i = 0; i < 4; i++) {
fb->pitches[i] = mode_cmd->pitches[i];
fb->offsets[i] = mode_cmd->offsets[i];
+ fb->modifier[i] = mode_cmd->modifier[i];
}
drm_fb_get_bpp_depth(mode_cmd->pixel_format, &fb->depth,
&fb->bits_per_pixel);
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 3785d66..a6d773a 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -321,6 +321,9 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_
else
req->value = 64;
break;
+ case DRM_CAP_ADDFB2_MODIFIERS:
+ req->value = dev->mode_config.allow_fb_modifiers;
+ break;
default:
return -EINVAL;
}
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 920e21a..b1465d6 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -202,6 +202,7 @@ struct drm_framebuffer {
const struct drm_framebuffer_funcs *funcs;
unsigned int pitches[4];
unsigned int offsets[4];
+ uint64_t modifier[4];
unsigned int width;
unsigned int height;
/* depth can be 15 or 16 */
@@ -1155,6 +1156,9 @@ struct drm_mode_config {
/* whether async page flip is supported or not */
bool async_page_flip;

+ /* whether the driver supports fb modifiers */
+ bool allow_fb_modifiers;
+
/* cursor size */
uint32_t cursor_width, cursor_height;
};
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 01b2d6d..ff6ef62 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -630,6 +630,7 @@ struct drm_gem_open {
*/
#define DRM_CAP_CURSOR_WIDTH 0x8
#define DRM_CAP_CURSOR_HEIGHT 0x9
+#define DRM_CAP_ADDFB2_MODIFIERS 0x10

/** DRM_IOCTL_GET_CAP ioctl argument type */
struct drm_get_cap {
diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
index 646ae5f..6221096 100644
--- a/include/uapi/drm/drm_fourcc.h
+++ b/include/uapi/drm/drm_fourcc.h
@@ -132,4 +132,36 @@
#define DRM_FORMAT_YUV444 fourcc_code('Y', 'U', '2', '4') /* non-subsampled Cb (1) and Cr (2) planes */
#define DRM_FORMAT_YVU444 fourcc_code('Y', 'V', '2', '4') /* non-subsampled Cr (1) and Cb (2) planes */

+
+/*
+ * Format Modifiers:
+ *
+ * Format modifiers describe, typically, a re-ordering or modification
+ * of the data in a plane of an FB. This can be used to express tiled/
+ * swizzled formats, or compression, or a combination of the two.
+ *
+ * The upper 8 bits of the format modifier are a vendor-id as assigned
+ * below. The lower 56 bits are assigned as vendor sees fit.
+ */
+
+/* Vendor Ids: */
+#define DRM_FORMAT_MOD_NONE 0
+#define DRM_FORMAT_MOD_VENDOR_INTEL 0x01
+#define DRM_FORMAT_MOD_VENDOR_AMD 0x02
+#define DRM_FORMAT_MOD_VENDOR_NV 0x03
+#define DRM_FORMAT_MOD_VENDOR_SAMSUNG 0x04
+#define DRM_FORMAT_MOD_VENDOR_QCOM 0x05
+/* add more to the end as needed */
+
+#define fourcc_mod_code(vendor, val) \
+ ((((u64)DRM_FORMAT_MOD_VENDOR_## vendor) << 56) | (val & 0x00ffffffffffffffL))
+
+/*
+ * Format Modifier tokens:
+ *
+ * When adding a new token please document the layout with a code comment,
+ * similar to the fourcc codes above. drm_fourcc.h is considered the
+ * authoritative source for all of these.
+ */
+
#endif /* DRM_FOURCC_H */
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index ca788e0..dbeba94 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -336,6 +336,7 @@ struct drm_mode_fb_cmd {
};

#define DRM_MODE_FB_INTERLACED (1<<0) /* for interlaced framebuffers */
+#define DRM_MODE_FB_MODIFIERS (1<<1) /* enables ->modifer[] */

struct drm_mode_fb_cmd2 {
__u32 fb_id;
@@ -356,10 +357,18 @@ struct drm_mode_fb_cmd2 {
* So it would consist of Y as offsets[0] and UV as
* offsets[1]. Note that offsets[0] will generally
* be 0 (but this is not required).
+ *
+ * To accommodate tiled, compressed, etc formats, a per-plane
+ * modifier can be specified. The default value of zero
+ * indicates "native" format as specified by the fourcc.
+ * Vendor specific modifier token. This allows, for example,
+ * different tiling/swizzling pattern on different planes.
+ * See discussion above of DRM_FORMAT_MOD_xxx.
*/
__u32 handles[4];
__u32 pitches[4]; /* pitch for each plane */
__u32 offsets[4]; /* offset of each plane */
+ __u64 modifier[4]; /* ie, tiling, compressed (per plane) */
};

#define DRM_MODE_FB_DIRTY_ANNOTATE_COPY 0x01
--
2.2.2