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.
v2: Add missing files lost in a rebase
v3: - Create separate file in Documentation/ABI/testing/, add it to MAINTAINERS - Fix kernel version (Daniel) - Remove unnecessary brackets (Jason) - Fix SPDX comment style
v4: improve sysfs code (Greg)
Signed-off-by: Simon Ser contact@emersion.fr Reviewed-by: Jason Ekstrand jason.ekstrand@collabora.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Bas Nieuwenhuizen bas@basnieuwenhuizen.nl Cc: Christian König christian.koenig@amd.com Cc: Greg KH greg@kroah.com --- .../ABI/testing/sysfs-kernel-dmabuf-caps | 13 ++++++ MAINTAINERS | 1 + drivers/dma-buf/Makefile | 2 +- drivers/dma-buf/dma-buf-sysfs-caps.c | 31 +++++++++++++ drivers/dma-buf/dma-buf-sysfs-caps.h | 15 +++++++ drivers/dma-buf/dma-buf-sysfs-stats.c | 16 ++----- drivers/dma-buf/dma-buf-sysfs-stats.h | 6 ++- drivers/dma-buf/dma-buf.c | 45 +++++++++++++++++-- include/uapi/linux/dma-buf.h | 6 +++ 9 files changed, 115 insertions(+), 20 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-kernel-dmabuf-caps create mode 100644 drivers/dma-buf/dma-buf-sysfs-caps.c create mode 100644 drivers/dma-buf/dma-buf-sysfs-caps.h
diff --git a/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps new file mode 100644 index 000000000000..f83af422fd18 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps @@ -0,0 +1,13 @@ +What: /sys/kernel/dmabuf/caps +Date: May 2022 +KernelVersion: v5.20 +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: v5.20 +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/MAINTAINERS b/MAINTAINERS index 11da16bfa123..8966686f7231 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5871,6 +5871,7 @@ L: dri-devel@lists.freedesktop.org L: linaro-mm-sig@lists.linaro.org (moderated for non-subscribers) S: Maintained T: git git://anongit.freedesktop.org/drm/drm-misc +F: Documentation/ABI/testing/sysfs-kernel-dmabuf-caps F: Documentation/driver-api/dma-buf.rst F: drivers/dma-buf/ F: include/linux/*fence.h 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-caps.c b/drivers/dma-buf/dma-buf-sysfs-caps.c new file mode 100644 index 000000000000..6eb27b81469f --- /dev/null +++ b/drivers/dma-buf/dma-buf-sysfs-caps.c @@ -0,0 +1,31 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * DMA-BUF sysfs capabilities. + * + * Copyright (C) 2022 Simon Ser + */ + +#include <linux/kobject.h> +#include <linux/sysfs.h> + +#include "dma-buf-sysfs-caps.h" + +static ssize_t sync_file_import_export_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sysfs_emit(buf, "1\n"); +} + +static struct kobj_attribute dma_buf_sync_file_import_export_attr = + __ATTR_RO(sync_file_import_export); + +static struct attribute *dma_buf_caps_attrs[] = { + &dma_buf_sync_file_import_export_attr.attr, + NULL, +}; + +const struct attribute_group dma_buf_caps_group = { + .name = "caps", + .attrs = dma_buf_caps_attrs, +}; diff --git a/drivers/dma-buf/dma-buf-sysfs-caps.h b/drivers/dma-buf/dma-buf-sysfs-caps.h new file mode 100644 index 000000000000..e40a93513f06 --- /dev/null +++ b/drivers/dma-buf/dma-buf-sysfs-caps.h @@ -0,0 +1,15 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * DMA-BUF sysfs capabilities. + * + * Copyright (C) 2022 Simon Ser + */ + +#ifndef _DMA_BUF_SYSFS_CAPS_H +#define _DMA_BUF_SYSFS_CAPS_H + +struct attribute_group; + +extern const struct attribute_group dma_buf_caps_group; + +#endif // _DMA_BUF_SYSFS_CAPS_H diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c index 2bba0babcb62..e2e62f83ce18 100644 --- a/drivers/dma-buf/dma-buf-sysfs-stats.c +++ b/drivers/dma-buf/dma-buf-sysfs-stats.c @@ -141,23 +141,14 @@ 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); - if (!dma_buf_per_buffer_stats_kset) { - kset_unregister(dma_buf_stats_kset); + &kset->kobj); + if (!dma_buf_per_buffer_stats_kset) return -ENOMEM; - }
return 0; } @@ -165,7 +156,6 @@ 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..61c5be57558e 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 +1547,57 @@ 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 const struct attribute_group *dma_buf_sysfs_groups[] = { + &dma_buf_caps_group, + NULL, +}; + +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 = sysfs_create_groups(&dma_buf_kset->kobj, dma_buf_sysfs_groups); if (ret) - return ret; + goto err_kset; + + ret = dma_buf_init_sysfs_statistics(dma_buf_kset); + if (ret) + goto err_kset;
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_kset: + kset_unregister(dma_buf_kset); + return ret; } subsys_initcall(dma_buf_init);
@@ -1570,5 +1606,6 @@ static void __exit dma_buf_deinit(void) dma_buf_uninit_debugfs(); kern_unmount(dma_buf_mnt); dma_buf_uninit_sysfs_statistics(); + 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 { /**