Linaro-mm-sig January 2014

linaro-mm-sig@lists.linaro.org

13 participants
7 discussions

by Thierry Reding

This is a simple test module that can be used to allocate, export and delete DMA-BUF objects. It can be used to test DMA-BUF sharing in systems that lack a real second driver. Signed-off-by: Thierry Reding <treding(a)nvidia.com> --- drivers/base/Kconfig | 4 + drivers/base/Makefile | 1 + drivers/base/dma-buf-test.c | 308 ++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 313 insertions(+) create mode 100644 drivers/base/dma-buf-test.c diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index e373671652b0..bed2abb9491b 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -200,6 +200,10 @@ config DMA_SHARED_BUFFER APIs extension; the file's descriptor can then be passed on to other driver. +config DMA_BUF_TEST + tristate "DMA-BUF test module" + depends on DMA_SHARED_BUFFER + config DMA_CMA bool "DMA Contiguous Memory Allocator" depends on HAVE_DMA_CONTIGUOUS && CMA diff --git a/drivers/base/Makefile b/drivers/base/Makefile index 94e8a80e87f8..cad983b6626f 100644 --- a/drivers/base/Makefile +++ b/drivers/base/Makefile @@ -25,3 +25,4 @@ obj-$(CONFIG_PINCTRL) += pinctrl.o ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG +obj-$(CONFIG_DMA_BUF_TEST) += dma-buf-test.o diff --git a/drivers/base/dma-buf-test.c b/drivers/base/dma-buf-test.c new file mode 100644 index 000000000000..f5498b74a09b --- /dev/null +++ b/drivers/base/dma-buf-test.c @@ -0,0 +1,308 @@ +#include <linux/dma-buf.h> +#include <linux/err.h> +#include <linux/fs.h> +#include <linux/miscdevice.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/uaccess.h> + +struct dmabuf_create { + __u32 flags; + __u32 size; +}; + +#define DMABUF_IOCTL_BASE 'D' +#define DMABUF_IOCTL_CREATE _IOWR(DMABUF_IOCTL_BASE, 0, struct dmabuf_create) +#define DMABUF_IOCTL_DELETE _IOWR(DMABUF_IOCTL_BASE, 1, int) +#define DMABUF_IOCTL_EXPORT _IOWR(DMABUF_IOCTL_BASE, 2, int) + +struct dmabuf_file { + struct dma_buf *buf; + dma_addr_t phys; + size_t size; + void *virt; +}; + +static int dmabuf_attach(struct dma_buf *buf, struct device *dev, + struct dma_buf_attachment *attach) +{ + return 0; +} + +static void dmabuf_detach(struct dma_buf *buf, + struct dma_buf_attachment *attach) +{ +} + +static struct sg_table *dmabuf_map_dma_buf(struct dma_buf_attachment *attach, + enum dma_data_direction dir) +{ + struct dmabuf_file *priv = attach->dmabuf->priv; + struct sg_table *sgt; + + sgt = kmalloc(sizeof(*sgt), GFP_KERNEL); + if (!sgt) + return NULL; + + if (sg_alloc_table(sgt, 1, GFP_KERNEL)) { + kfree(sgt); + return NULL; + } + + sg_dma_address(sgt->sgl) = priv->phys; + sg_dma_len(sgt->sgl) = priv->size; + + return sgt; +} + +static void dmabuf_unmap_dma_buf(struct dma_buf_attachment *attach, + struct sg_table *sgt, + enum dma_data_direction dir) +{ + sg_free_table(sgt); + kfree(sgt); +} + +static void dmabuf_release(struct dma_buf *buf) +{ +} + +static int dmabuf_begin_cpu_access(struct dma_buf *buf, size_t size, + size_t length, + enum dma_data_direction direction) +{ + return 0; +} + +static void dmabuf_end_cpu_access(struct dma_buf *buf, size_t size, + size_t length, + enum dma_data_direction direction) +{ +} + +static void *dmabuf_kmap_atomic(struct dma_buf *buf, unsigned long page) +{ + return NULL; +} + +static void dmabuf_kunmap_atomic(struct dma_buf *buf, unsigned long page, + void *vaddr) +{ +} + +static void *dmabuf_kmap(struct dma_buf *buf, unsigned long page) +{ + return NULL; +} + +static void dmabuf_kunmap(struct dma_buf *buf, unsigned long page, void *vaddr) +{ +} + +static void dmabuf_vm_open(struct vm_area_struct *vma) +{ +} + +static void dmabuf_vm_close(struct vm_area_struct *vma) +{ +} + +static int dmabuf_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + return 0; +} + +static const struct vm_operations_struct dmabuf_vm_ops = { + .open = dmabuf_vm_open, + .close = dmabuf_vm_close, + .fault = dmabuf_vm_fault, +}; + +static int dmabuf_mmap(struct dma_buf *buf, struct vm_area_struct *vma) +{ + pgprot_t prot = vm_get_page_prot(vma->vm_flags); + struct dmabuf_file *priv = buf->priv; + + vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; + vma->vm_ops = &dmabuf_vm_ops; + vma->vm_private_data = priv; + vma->vm_page_prot = pgprot_writecombine(prot); + + return remap_pfn_range(vma, vma->vm_start, priv->phys >> PAGE_SHIFT, + vma->vm_end - vma->vm_start, vma->vm_page_prot); +} + +static void *dmabuf_vmap(struct dma_buf *buf) +{ + return NULL; +} + +static void dmabuf_vunmap(struct dma_buf *buf, void *vaddr) +{ +} + +static const struct dma_buf_ops dmabuf_ops = { + .attach = dmabuf_attach, + .detach = dmabuf_detach, + .map_dma_buf = dmabuf_map_dma_buf, + .unmap_dma_buf = dmabuf_unmap_dma_buf, + .release = dmabuf_release, + .begin_cpu_access = dmabuf_begin_cpu_access, + .end_cpu_access = dmabuf_end_cpu_access, + .kmap_atomic = dmabuf_kmap_atomic, + .kunmap_atomic = dmabuf_kunmap_atomic, + .kmap = dmabuf_kmap, + .kunmap = dmabuf_kunmap, + .mmap = dmabuf_mmap, + .vmap = dmabuf_vmap, + .vunmap = dmabuf_vunmap, +}; + +static int dmabuf_file_open(struct inode *inode, struct file *file) +{ + struct dmabuf_file *priv; + int ret = 0; + + priv = kzalloc(sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + file->private_data = priv; + + return ret; +} + +static int dmabuf_file_release(struct inode *inode, struct file *file) +{ + struct dmabuf_file *priv = file->private_data; + int ret = 0; + + if (priv->virt) + dma_free_writecombine(NULL, priv->size, priv->virt, priv->phys); + + if (priv->buf) + dma_buf_put(priv->buf); + + kfree(priv); + + return ret; +} + +static int dmabuf_ioctl_create(struct dmabuf_file *priv, const void __user *data) +{ + struct dmabuf_create args; + int ret = 0; + + if (priv->buf || priv->virt) + return -EBUSY; + + if (copy_from_user(&args, data, sizeof(args))) + return -EFAULT; + + priv->virt = dma_alloc_writecombine(NULL, args.size, &priv->phys, + GFP_KERNEL | __GFP_NOWARN); + if (!priv->virt) + return -ENOMEM; + + priv->buf = dma_buf_export(priv, &dmabuf_ops, args.size, args.flags); + if (!priv->buf) { + ret = -ENOMEM; + goto free; + } + + if (IS_ERR(priv->buf)) { + ret = PTR_ERR(priv->buf); + goto free; + } + + priv->size = args.size; + + return 0; + +free: + dma_free_writecombine(NULL, priv->size, priv->virt, priv->phys); + priv->virt = NULL; + return ret; +} + +static int dmabuf_ioctl_delete(struct dmabuf_file *priv, unsigned long flags) +{ + dma_free_writecombine(NULL, priv->size, priv->virt, priv->phys); + priv->virt = NULL; + priv->phys = 0; + priv->size = 0; + + dma_buf_put(priv->buf); + priv->buf = NULL; + + return 0; +} + +static int dmabuf_ioctl_export(struct dmabuf_file *priv, unsigned long flags) +{ + int err; + + get_dma_buf(priv->buf); + + err = dma_buf_fd(priv->buf, flags); + if (err < 0) + dma_buf_put(priv->buf); + + return err; +} + +static long dmabuf_file_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct dmabuf_file *priv = file->private_data; + long ret = 0; + + switch (cmd) { + case DMABUF_IOCTL_CREATE: + ret = dmabuf_ioctl_create(priv, (const void __user *)arg); + break; + + case DMABUF_IOCTL_DELETE: + ret = dmabuf_ioctl_delete(priv, arg); + break; + + case DMABUF_IOCTL_EXPORT: + ret = dmabuf_ioctl_export(priv, arg); + break; + + default: + ret = -ENOTTY; + break; + } + + return ret; +} + +static const struct file_operations dmabuf_fops = { + .owner = THIS_MODULE, + .open = dmabuf_file_open, + .release = dmabuf_file_release, + .unlocked_ioctl = dmabuf_file_ioctl, +}; + +static struct miscdevice dmabuf_device = { + .minor = 128, + .name = "dmabuf", + .fops = &dmabuf_fops, +}; + +static int __init dmabuf_init(void) +{ + return misc_register(&dmabuf_device); +} +module_init(dmabuf_init); + +static void __exit dmabuf_exit(void) +{ + misc_deregister(&dmabuf_device); +} +module_exit(dmabuf_exit); + +MODULE_AUTHOR("Thierry Reding <treding(a)nvidia.com>"); +MODULE_DESCRIPTION("DMA-BUF test driver"); +MODULE_LICENSE("GPL v2"); -- 1.8.4.2

10 years, 9 months

CMA on AArch64

by Laura Abbott

Hi, I noticed there is currently no CMA support for AArch64. Is this already on someone's TODO list or is this still open? Thanks, Laura -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

10 years, 10 months

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

by Colin Cross

dma_buf_map_attachment and dma_buf_vmap can return NULL or ERR_PTR on a error. This encourages a common buggy pattern in callers: sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL); if (IS_ERR_OR_NULL(sgt)) return PTR_ERR(sgt); This causes the caller to return 0 on an error. IS_ERR_OR_NULL is almost always a sign of poorly-defined error handling. This patch converts dma_buf_map_attachment to always return ERR_PTR, and fixes the callers that incorrectly handled NULL. There are a few more callers that were not checking for NULL at all, which would have dereferenced a NULL pointer later. There are also a few more callers that correctly handled NULL and ERR_PTR differently, I left those alone but they could also be modified to delete the NULL check. This patch also converts dma_buf_vmap to always return NULL. All the callers to dma_buf_vmap only check for NULL, and would have dereferenced an ERR_PTR and panic'd if one was ever returned. This is not consistent with the rest of the dma buf APIs, but matches the expectations of all of the callers. Signed-off-by: Colin Cross <ccross(a)android.com> --- drivers/base/dma-buf.c | 18 +++++++++++------- drivers/gpu/drm/drm_prime.c | 2 +- drivers/gpu/drm/exynos/exynos_drm_dmabuf.c | 2 +- drivers/media/v4l2-core/videobuf2-dma-contig.c | 2 +- 4 files changed, 14 insertions(+), 10 deletions(-) diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c index 1e16cbd61da2..cfe1d8bc7bb8 100644 --- a/drivers/base/dma-buf.c +++ b/drivers/base/dma-buf.c @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put); * @dmabuf: [in] buffer to attach device to. * @dev: [in] device to be attached. * - * Returns struct dma_buf_attachment * for this attachment; may return negative - * error codes. - * + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on + * error. */ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev) @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach); * @attach: [in] attachment whose scatterlist is to be returned * @direction: [in] direction of DMA transfer * - * Returns sg_table containing the scatterlist to be returned; may return NULL - * or ERR_PTR. - * + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR + * on error. */ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, enum dma_data_direction direction) @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, return ERR_PTR(-EINVAL); sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); + if (!sg_table) + sg_table = ERR_PTR(-ENOMEM); return sg_table; } @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap); * These calls are optional in drivers. The intended use for them * is for mapping objects linear in kernel space for high use objects. * Please attempt to use kmap/kunmap before thinking about these interfaces. + * + * Returns NULL on error. */ void *dma_buf_vmap(struct dma_buf *dmabuf) { @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf) BUG_ON(dmabuf->vmap_ptr); ptr = dmabuf->ops->vmap(dmabuf); - if (IS_ERR_OR_NULL(ptr)) + if (WARN_ON_ONCE(IS_ERR(ptr))) + ptr = NULL; + if (!ptr) goto out_unlock; dmabuf->vmap_ptr = ptr; diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 56805c39c906..bb516fdd195d 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev, get_dma_buf(dma_buf); sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL); - if (IS_ERR_OR_NULL(sgt)) { + if (IS_ERR(sgt)) { ret = PTR_ERR(sgt); goto fail_detach; } diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c index 59827cc5e770..c786cd4f457b 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev, get_dma_buf(dma_buf); sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL); - if (IS_ERR_OR_NULL(sgt)) { + if (IS_ERR(sgt)) { ret = PTR_ERR(sgt); goto err_buf_detach; } diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c index 33d3871d1e13..880be0782dd9 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv) /* get the associated scatterlist for this buffer */ sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir); - if (IS_ERR_OR_NULL(sgt)) { + if (IS_ERR(sgt)) { pr_err("Error getting dmabuf scatterlist\n"); return -EINVAL; } -- 1.8.5.1

10 years, 10 months

[PATCH 0/7] dma-buf synchronization patches

by Maarten Lankhorst

The following series implements fence and converts dma-buf and android sync to use it. Patch 6 and 7 add support for polling to dma-buf, blocking until all fences are signaled. --- Maarten Lankhorst (7): sched: allow try_to_wake_up to be used internally outside of core.c fence: dma-buf cross-device synchronization (v16) seqno-fence: Hardware dma-buf implementation of fencing (v4) dma-buf: use reservation objects android: convert sync to fence api, v3 reservation: add support for fences to enable cross-device synchronisation dma-buf: add poll support Documentation/DocBook/device-drivers.tmpl | 3 drivers/base/Kconfig | 9 drivers/base/Makefile | 2 drivers/base/dma-buf.c | 124 +++ drivers/base/fence.c | 465 ++++++++++++ drivers/gpu/drm/drm_prime.c | 8 drivers/gpu/drm/exynos/exynos_drm_dmabuf.c | 2 drivers/gpu/drm/i915/i915_gem_dmabuf.c | 2 drivers/gpu/drm/nouveau/nouveau_drm.c | 1 drivers/gpu/drm/nouveau/nouveau_gem.h | 1 drivers/gpu/drm/nouveau/nouveau_prime.c | 7 drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c | 2 drivers/gpu/drm/radeon/radeon_drv.c | 2 drivers/gpu/drm/radeon/radeon_prime.c | 8 drivers/gpu/drm/ttm/ttm_object.c | 2 drivers/media/v4l2-core/videobuf2-dma-contig.c | 2 drivers/staging/android/Kconfig | 1 drivers/staging/android/Makefile | 2 drivers/staging/android/sw_sync.c | 4 drivers/staging/android/sync.c | 895 ++++++++---------------- drivers/staging/android/sync.h | 85 +- drivers/staging/android/sync_debug.c | 245 +++++++ drivers/staging/android/trace/sync.h | 12 include/drm/drmP.h | 2 include/linux/dma-buf.h | 21 - include/linux/fence.h | 329 +++++++++ include/linux/reservation.h | 18 include/linux/seqno-fence.h | 109 +++ include/linux/wait.h | 1 include/trace/events/fence.h | 125 +++ kernel/sched/core.c | 2 31 files changed, 1825 insertions(+), 666 deletions(-) create mode 100644 drivers/base/fence.c create mode 100644 drivers/staging/android/sync_debug.c create mode 100644 include/linux/fence.h create mode 100644 include/linux/seqno-fence.h create mode 100644 include/trace/events/fence.h -- Signature

10 years, 11 months

[RFC] dma-mapping: Provide write-combine allocations

by Thierry Reding

Provide an implementation for dma_{alloc,free}_writecombine() when the architecture supports DMA attributes. Signed-off-by: Thierry Reding <treding(a)nvidia.com> --- arch/arm/include/asm/dma-mapping.h | 16 ---------------- include/linux/dma-mapping.h | 16 ++++++++++++++++ 2 files changed, 16 insertions(+), 16 deletions(-) diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h index e701a4d9aa59..96b7634a7edc 100644 --- a/arch/arm/include/asm/dma-mapping.h +++ b/arch/arm/include/asm/dma-mapping.h @@ -242,22 +242,6 @@ extern int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma, void *cpu_addr, dma_addr_t dma_addr, size_t size, struct dma_attrs *attrs); -static inline void *dma_alloc_writecombine(struct device *dev, size_t size, - dma_addr_t *dma_handle, gfp_t flag) -{ - DEFINE_DMA_ATTRS(attrs); - dma_set_attr(DMA_ATTR_WRITE_COMBINE, &attrs); - return dma_alloc_attrs(dev, size, dma_handle, flag, &attrs); -} - -static inline void dma_free_writecombine(struct device *dev, size_t size, - void *cpu_addr, dma_addr_t dma_handle) -{ - DEFINE_DMA_ATTRS(attrs); - dma_set_attr(DMA_ATTR_WRITE_COMBINE, &attrs); - return dma_free_attrs(dev, size, cpu_addr, dma_handle, &attrs); -} - /* * This can be called during early boot to increase the size of the atomic * coherent DMA pool above the default value of 256KiB. It must be called diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index fd4aee29ad10..8475e02b4bd1 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -249,6 +249,22 @@ struct dma_attrs; #define dma_unmap_sg_attrs(dev, sgl, nents, dir, attrs) \ dma_unmap_sg(dev, sgl, nents, dir) +#else +static inline void *dma_alloc_writecombine(struct device *dev, size_t size, + dma_addr_t *dma_addr, gfp_t gfp) +{ + DEFINE_DMA_ATTRS(attrs); + dma_set_attr(DMA_ATTR_WRITE_COMBINE, &attrs); + return dma_alloc_attrs(dev, size, dma_addr, gfp, &attrs); +} + +static inline void dma_free_writecombine(struct device *dev, size_t size, + void *cpu_addr, dma_addr_t dma_addr) +{ + DEFINE_DMA_ATTRS(attrs); + dma_set_attr(DMA_ATTR_WRITE_COMBINE, &attrs); + return dma_free_attrs(dev, size, cpu_addr, dma_addr, &attrs); +} #endif /* CONFIG_HAVE_DMA_ATTRS */ #ifdef CONFIG_NEED_DMA_MAP_STATE -- 1.8.4.2

10 years, 11 months

[PATCH v4 0/3] Add support of dmabuf in wayland/weston

by benjamin.gaignard＠linaro.org

From: Benjamin Gaignard <benjamin.gaignard(a)linaro.org> The goal of this serie of patches is to add a way to use dmabuf file descriptor inside wayland and weston. In a context where there is no Mesa EGL (and so no wl_drm protocol) wl_dmabuf could be used as an alternative to shm to share buffers between hardware devices. If your hardware device (video decoder, renderer, etc...) need physical contiguous memory (obviously don't have MMU) wl_dmabuf may save the cost of one copy compare to shm. shm case: videodecoder --(copy into shm_buffer)--> weston(+pixman) --> HW renderer dmabuf case: videodecoder --(directly write in dmabuf buffer)--> weston(+pixman) --> HW renderer The server is responsible to send its supported pixel formats and the device name to be used by the client to allocate buffers. While mmap() call on dmabuf file descriptor result isn't guaranty on all architectures both server and client should take care of it before accessing to buffer data to avoid segfault. This series of patches include wayland and weston modifications. An example of how use wl_dmabuf is provided in weston/clients/simple-dmabuf.c === Wayland === Benjamin Gaignard (1): Add wl_dmabuf protocol protocol/Makefile.am | 6 +- protocol/wayland-dmabuf.xml | 128 ++++++++++++++++++++++++ src/Makefile.am | 12 ++- src/wayland-dmabuf.c | 231 +++++++++++++++++++++++++++++++++++++++++++ src/wayland-dmabuf.h | 123 +++++++++++++++++++++++ 5 files changed, 496 insertions(+), 4 deletions(-) create mode 100644 protocol/wayland-dmabuf.xml create mode 100644 src/wayland-dmabuf.c create mode 100644 src/wayland-dmabuf.h === Weston === Benjamin Gaignard (2): compositor-drm: allow to be a wl_dmabuf server add simple-dmabuf client clients/Makefile.am | 11 ++ clients/simple-dmabuf.c | 469 +++++++++++++++++++++++++++++++++++++++++++++++ configure.ac | 5 + src/compositor-drm.c | 83 ++++++++- src/compositor.c | 4 +- src/compositor.h | 2 + src/pixman-renderer.c | 93 +++++++--- 7 files changed, 637 insertions(+), 30 deletions(-) create mode 100644 clients/simple-dmabuf.c -- 1.7.9.5

10 years, 11 months

Specifying subrect properties in dma-buf

by Sundareson, Prabindh

Hello all, I have an use-case, where a buffer "B" needs to be further operated upon by an additional operator (ex, CPU or 2D HW). The further operation is typically in smaller subrects of "B". While looking through the dma-buf API, I do not see a way by which I can specify properties of subrects in a buffer which can be specified as "read-only" to one user of the buffer, while the other user can go ahead and update it. If we have this mechanism, we can do below steps to reduce latency of locking/waiting for one full buffer update, and then making it available to the next consumer. (1) Create dma-buf using usual methods (2) Exported to 2 users - ex GPU, and 2D HW (3) GPU updates specific subrects (4) 2D HW updates specific subrects (5) When both (3) and (4) are complete, the buffer is available to next consumer. Since (3) and (4) can run in parallel, latency can be reduced. If there is a way by which this can already be done, I would appreciate if someone can point me to it. regards Prabindh

10 years, 11 months

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Linaro-mm-sig January 2014