Re: [PATCH] dma-buf: Expose buffer size to userspace (v2)
Le 04/09/2013 14:05, Daniel Vetter a écrit : On Wed, Sep 04, 2013 at 12:24:27PM +0200, Martin Peres wrote: Hi Christopher, Le 04/09/2013 05:15, Christopher James Halse Rogers a écrit : Each dma-buf has an associated size and it's reasonable for userspace to want to know what it is. Since userspace already has an fd, expose the size using the size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0); idiom. v2: Added Daniel's sugeested documentation, with minor fixups Signed-off-by: Christopher James Halse Rogers Reviewed-by: Daniel Vetter Tested-by: Daniel Vetter --- Documentation/dma-buf-sharing.txt | 12 drivers/base/dma-buf.c| 28 2 files changed, 40 insertions(+) diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 0b23261..849e982 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: interesting ways depending upong the exporter (if userspace starts depending upon this implicit synchronization). +Other Interfaces Exposed to Userspace on the dma-buf FD +-- + +- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only + with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow + the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other + llseek operation will report -EINVAL. + + If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all Shouldn't it be "supported" instead of "support"? Anyway, I'm just curious, in which case is it important to know the size? Do we already have a way to get the dimensions (x, y and stripe)? Size is an invariant part of a dma-buf. Everything else wrt metadata isn't tracked in the kernel, so doesn't make much sense to expose it ;-) -Daniel ACK, thanks Daniel. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] dma-buf: Expose buffer size to userspace (v2)
On Wed, Sep 04, 2013 at 12:24:27PM +0200, Martin Peres wrote: > Hi Christopher, > Le 04/09/2013 05:15, Christopher James Halse Rogers a écrit : > >Each dma-buf has an associated size and it's reasonable for userspace > >to want to know what it is. > > > >Since userspace already has an fd, expose the size using the > >size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0); > >idiom. > > > >v2: Added Daniel's sugeested documentation, with minor fixups > > > >Signed-off-by: Christopher James Halse Rogers > > > >Reviewed-by: Daniel Vetter > >Tested-by: Daniel Vetter > >--- > > Documentation/dma-buf-sharing.txt | 12 > > drivers/base/dma-buf.c| 28 > > 2 files changed, 40 insertions(+) > > > >diff --git a/Documentation/dma-buf-sharing.txt > >b/Documentation/dma-buf-sharing.txt > >index 0b23261..849e982 100644 > >--- a/Documentation/dma-buf-sharing.txt > >+++ b/Documentation/dma-buf-sharing.txt > >@@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has > >2 main use-cases: > > interesting ways depending upong the exporter (if userspace starts > > depending > > upon this implicit synchronization). > >+Other Interfaces Exposed to Userspace on the dma-buf FD > >+-- > >+ > >+- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only > >+ with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow > >+ the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every > >other > >+ llseek operation will report -EINVAL. > >+ > >+ If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for > >all > Shouldn't it be "supported" instead of "support"? > > Anyway, I'm just curious, in which case is it important to know the size? > Do we already have a way to get the dimensions (x, y and stripe)? Size is an invariant part of a dma-buf. Everything else wrt metadata isn't tracked in the kernel, so doesn't make much sense to expose it ;-) -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] dma-buf: Expose buffer size to userspace (v2)
Hi Christopher, Le 04/09/2013 05:15, Christopher James Halse Rogers a écrit : Each dma-buf has an associated size and it's reasonable for userspace to want to know what it is. Since userspace already has an fd, expose the size using the size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0); idiom. v2: Added Daniel's sugeested documentation, with minor fixups Signed-off-by: Christopher James Halse Rogers Reviewed-by: Daniel Vetter Tested-by: Daniel Vetter --- Documentation/dma-buf-sharing.txt | 12 drivers/base/dma-buf.c| 28 2 files changed, 40 insertions(+) diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 0b23261..849e982 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: interesting ways depending upong the exporter (if userspace starts depending upon this implicit synchronization). +Other Interfaces Exposed to Userspace on the dma-buf FD +-- + +- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only + with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow + the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other + llseek operation will report -EINVAL. + + If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all Shouldn't it be "supported" instead of "support"? Anyway, I'm just curious, in which case is it important to know the size? Do we already have a way to get the dimensions (x, y and stripe)? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] dma-buf: Expose buffer size to userspace (v2)
Hi Christopher, Le 04/09/2013 05:15, Christopher James Halse Rogers a écrit : Each dma-buf has an associated size and it's reasonable for userspace to want to know what it is. Since userspace already has an fd, expose the size using the size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0); idiom. v2: Added Daniel's sugeested documentation, with minor fixups Signed-off-by: Christopher James Halse Rogers christopher.halse.rog...@canonical.com Reviewed-by: Daniel Vetter daniel.vet...@ffwll.ch Tested-by: Daniel Vetter daniel.vet...@ffwll.ch --- Documentation/dma-buf-sharing.txt | 12 drivers/base/dma-buf.c| 28 2 files changed, 40 insertions(+) diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 0b23261..849e982 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: interesting ways depending upong the exporter (if userspace starts depending upon this implicit synchronization). +Other Interfaces Exposed to Userspace on the dma-buf FD +-- + +- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only + with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow + the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other + llseek operation will report -EINVAL. + + If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all Shouldn't it be supported instead of support? Anyway, I'm just curious, in which case is it important to know the size? Do we already have a way to get the dimensions (x, y and stripe)? -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] dma-buf: Expose buffer size to userspace (v2)
On Wed, Sep 04, 2013 at 12:24:27PM +0200, Martin Peres wrote: Hi Christopher, Le 04/09/2013 05:15, Christopher James Halse Rogers a écrit : Each dma-buf has an associated size and it's reasonable for userspace to want to know what it is. Since userspace already has an fd, expose the size using the size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0); idiom. v2: Added Daniel's sugeested documentation, with minor fixups Signed-off-by: Christopher James Halse Rogers christopher.halse.rog...@canonical.com Reviewed-by: Daniel Vetter daniel.vet...@ffwll.ch Tested-by: Daniel Vetter daniel.vet...@ffwll.ch --- Documentation/dma-buf-sharing.txt | 12 drivers/base/dma-buf.c| 28 2 files changed, 40 insertions(+) diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 0b23261..849e982 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: interesting ways depending upong the exporter (if userspace starts depending upon this implicit synchronization). +Other Interfaces Exposed to Userspace on the dma-buf FD +-- + +- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only + with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow + the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other + llseek operation will report -EINVAL. + + If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all Shouldn't it be supported instead of support? Anyway, I'm just curious, in which case is it important to know the size? Do we already have a way to get the dimensions (x, y and stripe)? Size is an invariant part of a dma-buf. Everything else wrt metadata isn't tracked in the kernel, so doesn't make much sense to expose it ;-) -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] dma-buf: Expose buffer size to userspace (v2)
Le 04/09/2013 14:05, Daniel Vetter a écrit : On Wed, Sep 04, 2013 at 12:24:27PM +0200, Martin Peres wrote: Hi Christopher, Le 04/09/2013 05:15, Christopher James Halse Rogers a écrit : Each dma-buf has an associated size and it's reasonable for userspace to want to know what it is. Since userspace already has an fd, expose the size using the size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0); idiom. v2: Added Daniel's sugeested documentation, with minor fixups Signed-off-by: Christopher James Halse Rogers christopher.halse.rog...@canonical.com Reviewed-by: Daniel Vetter daniel.vet...@ffwll.ch Tested-by: Daniel Vetter daniel.vet...@ffwll.ch --- Documentation/dma-buf-sharing.txt | 12 drivers/base/dma-buf.c| 28 2 files changed, 40 insertions(+) diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 0b23261..849e982 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: interesting ways depending upong the exporter (if userspace starts depending upon this implicit synchronization). +Other Interfaces Exposed to Userspace on the dma-buf FD +-- + +- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only + with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow + the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other + llseek operation will report -EINVAL. + + If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all Shouldn't it be supported instead of support? Anyway, I'm just curious, in which case is it important to know the size? Do we already have a way to get the dimensions (x, y and stripe)? Size is an invariant part of a dma-buf. Everything else wrt metadata isn't tracked in the kernel, so doesn't make much sense to expose it ;-) -Daniel ACK, thanks Daniel. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] dma-buf: Expose buffer size to userspace (v2)
Each dma-buf has an associated size and it's reasonable for userspace
to want to know what it is.
Since userspace already has an fd, expose the size using the
size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0);
idiom.
v2: Added Daniel's sugeested documentation, with minor fixups
Signed-off-by: Christopher James Halse Rogers
Reviewed-by: Daniel Vetter
Tested-by: Daniel Vetter
---
Documentation/dma-buf-sharing.txt | 12
drivers/base/dma-buf.c| 28
2 files changed, 40 insertions(+)
diff --git a/Documentation/dma-buf-sharing.txt
b/Documentation/dma-buf-sharing.txt
index 0b23261..849e982 100644
--- a/Documentation/dma-buf-sharing.txt
+++ b/Documentation/dma-buf-sharing.txt
@@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2
main use-cases:
interesting ways depending upong the exporter (if userspace starts depending
upon this implicit synchronization).
+Other Interfaces Exposed to Userspace on the dma-buf FD
+--
+
+- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only
+ with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow
+ the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other
+ llseek operation will report -EINVAL.
+
+ If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all
+ cases. Userspace can use this to detect support for discovering the dma-buf
+ size using llseek.
+
Miscellaneous notes
---
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 6687ba7..c33a857 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -77,9 +77,36 @@ static int dma_buf_mmap_internal(struct file *file, struct
vm_area_struct *vma)
return dmabuf->ops->mmap(dmabuf, vma);
}
+static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
+{
+ struct dma_buf *dmabuf;
+ loff_t base;
+
+ if (!is_dma_buf_file(file))
+ return -EBADF;
+
+ dmabuf = file->private_data;
+
+ /* only support discovering the end of the buffer,
+ but also allow SEEK_SET to maintain the idiomatic
+ SEEK_END(0), SEEK_CUR(0) pattern */
+ if (whence == SEEK_END)
+ base = dmabuf->size;
+ else if (whence == SEEK_SET)
+ base = 0;
+ else
+ return -EINVAL;
+
+ if (offset != 0)
+ return -EINVAL;
+
+ return base + offset;
+}
+
static const struct file_operations dma_buf_fops = {
.release= dma_buf_release,
.mmap = dma_buf_mmap_internal,
+ .llseek = dma_buf_llseek,
};
/*
@@ -133,6 +160,7 @@ struct dma_buf *dma_buf_export_named(void *priv, const
struct dma_buf_ops *ops,
dmabuf->exp_name = exp_name;
file = anon_inode_getfile("dmabuf", _buf_fops, dmabuf, flags);
+ file->f_mode |= FMODE_LSEEK;
dmabuf->file = file;
--
1.8.3.2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] dma-buf: Expose buffer size to userspace (v2)
Each dma-buf has an associated size and it's reasonable for userspace
to want to know what it is.
Since userspace already has an fd, expose the size using the
size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0);
idiom.
v2: Added Daniel's sugeested documentation, with minor fixups
Signed-off-by: Christopher James Halse Rogers
christopher.halse.rog...@canonical.com
Reviewed-by: Daniel Vetter daniel.vet...@ffwll.ch
Tested-by: Daniel Vetter daniel.vet...@ffwll.ch
---
Documentation/dma-buf-sharing.txt | 12
drivers/base/dma-buf.c| 28
2 files changed, 40 insertions(+)
diff --git a/Documentation/dma-buf-sharing.txt
b/Documentation/dma-buf-sharing.txt
index 0b23261..849e982 100644
--- a/Documentation/dma-buf-sharing.txt
+++ b/Documentation/dma-buf-sharing.txt
@@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2
main use-cases:
interesting ways depending upong the exporter (if userspace starts depending
upon this implicit synchronization).
+Other Interfaces Exposed to Userspace on the dma-buf FD
+--
+
+- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only
+ with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow
+ the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other
+ llseek operation will report -EINVAL.
+
+ If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all
+ cases. Userspace can use this to detect support for discovering the dma-buf
+ size using llseek.
+
Miscellaneous notes
---
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 6687ba7..c33a857 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -77,9 +77,36 @@ static int dma_buf_mmap_internal(struct file *file, struct
vm_area_struct *vma)
return dmabuf-ops-mmap(dmabuf, vma);
}
+static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
+{
+ struct dma_buf *dmabuf;
+ loff_t base;
+
+ if (!is_dma_buf_file(file))
+ return -EBADF;
+
+ dmabuf = file-private_data;
+
+ /* only support discovering the end of the buffer,
+ but also allow SEEK_SET to maintain the idiomatic
+ SEEK_END(0), SEEK_CUR(0) pattern */
+ if (whence == SEEK_END)
+ base = dmabuf-size;
+ else if (whence == SEEK_SET)
+ base = 0;
+ else
+ return -EINVAL;
+
+ if (offset != 0)
+ return -EINVAL;
+
+ return base + offset;
+}
+
static const struct file_operations dma_buf_fops = {
.release= dma_buf_release,
.mmap = dma_buf_mmap_internal,
+ .llseek = dma_buf_llseek,
};
/*
@@ -133,6 +160,7 @@ struct dma_buf *dma_buf_export_named(void *priv, const
struct dma_buf_ops *ops,
dmabuf-exp_name = exp_name;
file = anon_inode_getfile(dmabuf, dma_buf_fops, dmabuf, flags);
+ file-f_mode |= FMODE_LSEEK;
dmabuf-file = file;
--
1.8.3.2
--
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More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
