To discover support for new DMA-BUF IOCTLs, user-space has no choice but to try to perform the IOCTL on an existing DMA-BUF. However, user-space may want to figure out whether or not the IOCTL is available before it has a DMA-BUF at hand, e.g. at initialization time in a Wayland compositor.
Add a /sys/kernel/dmabuf/caps directory which allows the DMA-BUF subsystem to advertise supported features. Add a sync_file_import_export entry which indicates that importing and exporting sync_files from/to DMA-BUFs is supported.
Signed-off-by: Simon Ser contact@emersion.fr Cc: Jason Ekstrand jason@jlekstrand.net Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Bas Nieuwenhuizen bas@basnieuwenhuizen.nl Cc: Christian König christian.koenig@amd.com ---
This depends on: https://patchwork.freedesktop.org/series/103715/
.../ABI/testing/sysfs-kernel-dmabuf-buffers | 14 ++++++ drivers/dma-buf/Makefile | 2 +- drivers/dma-buf/dma-buf-sysfs-stats.c | 13 +----- drivers/dma-buf/dma-buf-sysfs-stats.h | 6 ++- drivers/dma-buf/dma-buf.c | 43 +++++++++++++++++-- include/uapi/linux/dma-buf.h | 6 +++ 6 files changed, 66 insertions(+), 18 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers b/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers index 5d3bc997dc64..682d313689d8 100644 --- a/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers +++ b/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers @@ -22,3 +22,17 @@ KernelVersion: v5.13 Contact: Hridya Valsaraju hridya@google.com Description: This file is read-only and specifies the size of the DMA-BUF in bytes. + +What: /sys/kernel/dmabuf/caps +Date: May 2022 +KernelVersion: v5.19 +Contact: Simon Ser contact@emersion.fr +Description: This directory advertises DMA-BUF capabilities supported by the + kernel. + +What: /sys/kernel/dmabuf/caps/sync_file_import_export +Date: May 2022 +KernelVersion: v5.19 +Contact: Simon Ser contact@emersion.fr +Description: This file is read-only and advertises support for importing and + exporting sync_files from/to DMA-BUFs. diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile index 4c9eb53ba3f8..afc874272710 100644 --- a/drivers/dma-buf/Makefile +++ b/drivers/dma-buf/Makefile @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \ - dma-resv.o + dma-resv.o dma-buf-sysfs-caps.o obj-$(CONFIG_DMABUF_HEAPS) += dma-heap.o obj-$(CONFIG_DMABUF_HEAPS) += heaps/ obj-$(CONFIG_SYNC_FILE) += sync_file.o diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c index 2bba0babcb62..09e43c8891d6 100644 --- a/drivers/dma-buf/dma-buf-sysfs-stats.c +++ b/drivers/dma-buf/dma-buf-sysfs-stats.c @@ -141,21 +141,13 @@ static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = { .filter = dmabuf_sysfs_uevent_filter, };
-static struct kset *dma_buf_stats_kset; static struct kset *dma_buf_per_buffer_stats_kset; -int dma_buf_init_sysfs_statistics(void) +int dma_buf_init_sysfs_statistics(struct kset *kset) { - dma_buf_stats_kset = kset_create_and_add("dmabuf", - &dmabuf_sysfs_no_uevent_ops, - kernel_kobj); - if (!dma_buf_stats_kset) - return -ENOMEM; - dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers", &dmabuf_sysfs_no_uevent_ops, - &dma_buf_stats_kset->kobj); + &kset->kobj); if (!dma_buf_per_buffer_stats_kset) { - kset_unregister(dma_buf_stats_kset); return -ENOMEM; }
@@ -165,7 +157,6 @@ int dma_buf_init_sysfs_statistics(void) void dma_buf_uninit_sysfs_statistics(void) { kset_unregister(dma_buf_per_buffer_stats_kset); - kset_unregister(dma_buf_stats_kset); }
int dma_buf_stats_setup(struct dma_buf *dmabuf) diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.h b/drivers/dma-buf/dma-buf-sysfs-stats.h index a49c6e2650cc..798c54fb8ee3 100644 --- a/drivers/dma-buf/dma-buf-sysfs-stats.h +++ b/drivers/dma-buf/dma-buf-sysfs-stats.h @@ -8,9 +8,11 @@ #ifndef _DMA_BUF_SYSFS_STATS_H #define _DMA_BUF_SYSFS_STATS_H
+struct kset; + #ifdef CONFIG_DMABUF_SYSFS_STATS
-int dma_buf_init_sysfs_statistics(void); +int dma_buf_init_sysfs_statistics(struct kset *kset); void dma_buf_uninit_sysfs_statistics(void);
int dma_buf_stats_setup(struct dma_buf *dmabuf); @@ -18,7 +20,7 @@ int dma_buf_stats_setup(struct dma_buf *dmabuf); void dma_buf_stats_teardown(struct dma_buf *dmabuf); #else
-static inline int dma_buf_init_sysfs_statistics(void) +static inline int dma_buf_init_sysfs_statistics(struct kset *kset) { return 0; } diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 5e1b0534b3ce..b5c5a5050508 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -30,6 +30,7 @@ #include <uapi/linux/dma-buf.h> #include <uapi/linux/magic.h>
+#include "dma-buf-sysfs-caps.h" #include "dma-buf-sysfs-stats.h"
static inline int is_dma_buf_file(struct file *); @@ -1546,22 +1547,54 @@ static inline void dma_buf_uninit_debugfs(void) } #endif
+/* Capabilities and statistics files do not need to send uevents. */ +static int dmabuf_sysfs_uevent_filter(struct kobject *kobj) +{ + return 0; +} + +static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = { + .filter = dmabuf_sysfs_uevent_filter, +}; + +static struct kset *dma_buf_kset; + static int __init dma_buf_init(void) { int ret;
- ret = dma_buf_init_sysfs_statistics(); + dma_buf_kset = kset_create_and_add("dmabuf", + &dmabuf_sysfs_no_uevent_ops, + kernel_kobj); + if (!dma_buf_kset) + return -ENOMEM; + + ret = dma_buf_init_sysfs_capabilities(dma_buf_kset); if (ret) - return ret; + goto err_kset; + + ret = dma_buf_init_sysfs_statistics(dma_buf_kset); + if (ret) + goto err_sysfs_caps;
dma_buf_mnt = kern_mount(&dma_buf_fs_type); - if (IS_ERR(dma_buf_mnt)) - return PTR_ERR(dma_buf_mnt); + if (IS_ERR(dma_buf_mnt)) { + ret = PTR_ERR(dma_buf_mnt); + goto err_sysfs_stats; + }
mutex_init(&db_list.lock); INIT_LIST_HEAD(&db_list.head); dma_buf_init_debugfs(); return 0; + +err_sysfs_stats: + dma_buf_uninit_sysfs_statistics(); +err_sysfs_caps: + dma_buf_uninit_sysfs_capabilities(); +err_kset: + kset_unregister(dma_buf_kset); + return ret; } subsys_initcall(dma_buf_init);
@@ -1570,5 +1603,7 @@ static void __exit dma_buf_deinit(void) dma_buf_uninit_debugfs(); kern_unmount(dma_buf_mnt); dma_buf_uninit_sysfs_statistics(); + dma_buf_uninit_sysfs_capabilities(); + kset_unregister(dma_buf_kset); } __exitcall(dma_buf_deinit); diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h index 70e213a0d7d9..ab3afd5da75a 100644 --- a/include/uapi/linux/dma-buf.h +++ b/include/uapi/linux/dma-buf.h @@ -114,6 +114,9 @@ struct dma_buf_sync { * ordering via these fences, it is the respnosibility of userspace to use * locks or other mechanisms to ensure that no other context adds fences or * submits work between steps 1 and 3 above. + * + * Userspace can check the availability of this API via + * /sys/kernel/dmabuf/caps/sync_file_import_export. */ struct dma_buf_export_sync_file { /** @@ -146,6 +149,9 @@ struct dma_buf_export_sync_file { * synchronized APIs such as Vulkan to inter-op with dma-buf consumers * which expect implicit synchronization such as OpenGL or most media * drivers/video. + * + * Userspace can check the availability of this API via + * /sys/kernel/dmabuf/caps/sync_file_import_export. */ struct dma_buf_import_sync_file { /**