[PATCH v2] RFC: framebuffer: provide generic get_fb_unmapped_area

Subsystems: framebuffer layer, the rest

STALE4597d

4 messages, 3 authors, 2014-03-17 · open the first message on its own page

[PATCH v2] RFC: framebuffer: provide generic get_fb_unmapped_area

From: Uwe Kleine-König <hidden>
Date: 2014-02-03 17:14:44

This patch makes mmapping the simple-framebuffer device work on a no-MMU
ARM target. The code is mostly taken from
arch/blackfin/kernel/sys_bfin.c.

Signed-off-by: Uwe Kleine-KÃ¶nig <redacted>
---
Hello,

note this is only tested on this no-MMU machine and I don't know enough
about framebuffers and mm to decide if this patch is sane. Also I'm
a bit unsure about the size check, I just believed Geert that
PAGE_ALIGN(info->fix.smem_len) is the right value to check against.

Best regards
Uwe

 drivers/video/fbmem.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 7309ac704e26..d0ccedafec8c 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c

@@ -1491,6 +1491,22 @@ __releases(&info->lock)
 	return 0;
 }
 
+#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
+#define fb_get_unmapped_area get_fb_unmapped_area
+#else
+unsigned long fb_get_unmapped_area(struct file *filp, unsigned long orig_addr,
+		unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+	struct fb_info * const info = filp->private_data;
+	unsigned long fb_size = PAGE_ALIGN(info->fix.smem_len);
+
+	if (pgoff > fb_size || len > fb_size - pgoff)
+		return -EINVAL;
+
+	return (unsigned long)info->screen_base + pgoff;
+}
+#endif
+
 static const struct file_operations fb_fops = {
 	.owner =	THIS_MODULE,
 	.read =		fb_read,

@@ -1502,9 +1518,7 @@ static const struct file_operations fb_fops = {
 	.mmap =		fb_mmap,
 	.open =		fb_open,
 	.release =	fb_release,
-#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
-	.get_unmapped_area = get_fb_unmapped_area,
-#endif
+	.get_unmapped_area = fb_get_unmapped_area,
 #ifdef CONFIG_FB_DEFERRED_IO
 	.fsync =	fb_deferred_io_fsync,
 #endif

-- 
1.8.5.2

Re: [PATCH v2] RFC: framebuffer: provide generic get_fb_unmapped_area

From: Uwe Kleine-König <hidden>
Date: 2014-03-14 21:06:13

On Mon, Feb 03, 2014 at 06:14:44PM +0100, Uwe Kleine-König wrote:

This patch makes mmapping the simple-framebuffer device work on a no-MMU
ARM target. The code is mostly taken from
arch/blackfin/kernel/sys_bfin.c.

Signed-off-by: Uwe Kleine-König <redacted>
---
Hello,

note this is only tested on this no-MMU machine and I don't know enough
about framebuffers and mm to decide if this patch is sane. Also I'm
a bit unsure about the size check, I just believed Geert that
PAGE_ALIGN(info->fix.smem_len) is the right value to check against.

Do you still have this patch on your radar?

Best regards
Uwe

quoted hunk

 drivers/video/fbmem.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 7309ac704e26..d0ccedafec8c 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c

@@ -1491,6 +1491,22 @@ __releases(&info->lock)
 	return 0;
 }
 
+#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
+#define fb_get_unmapped_area get_fb_unmapped_area
+#else
+unsigned long fb_get_unmapped_area(struct file *filp, unsigned long orig_addr,
+		unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+	struct fb_info * const info = filp->private_data;
+	unsigned long fb_size = PAGE_ALIGN(info->fix.smem_len);
+
+	if (pgoff > fb_size || len > fb_size - pgoff)
+		return -EINVAL;
+
+	return (unsigned long)info->screen_base + pgoff;
+}
+#endif
+
 static const struct file_operations fb_fops = {
 	.owner =	THIS_MODULE,
 	.read =		fb_read,

@@ -1502,9 +1518,7 @@ static const struct file_operations fb_fops = {
 	.mmap =		fb_mmap,
 	.open =		fb_open,
 	.release =	fb_release,
-#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
-	.get_unmapped_area = get_fb_unmapped_area,
-#endif
+	.get_unmapped_area = fb_get_unmapped_area,
 #ifdef CONFIG_FB_DEFERRED_IO
 	.fsync =	fb_deferred_io_fsync,
 #endif

-- 
1.8.5.2

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

Re: [PATCH v2] RFC: framebuffer: provide generic get_fb_unmapped_area

From: Tomi Valkeinen <hidden>
Date: 2014-03-17 11:23:39

Hi,

On 03/02/14 19:14, Uwe Kleine-König wrote:

This patch makes mmapping the simple-framebuffer device work on a no-MMU
ARM target. The code is mostly taken from
arch/blackfin/kernel/sys_bfin.c.

Signed-off-by: Uwe Kleine-König <redacted>
---
Hello,

note this is only tested on this no-MMU machine and I don't know enough
about framebuffers and mm to decide if this patch is sane. Also I'm
a bit unsure about the size check, I just believed Geert that
PAGE_ALIGN(info->fix.smem_len) is the right value to check against.

I don't know enough about mm to say much here, and the text above make
me feel a bit uneasy. I'd be happy if this would get a few
acks/reviewed-bys/tested-bys...

So what does this patch actually do? If I read things correctly,
currently .get_unmapped_area is null, except for sparc and blackfin. But
userspace's mmap() calls that, right? Is there a default implementation
somewhere? Why is that different for no-MMU case?

 Tomi

Re: [PATCH v2] RFC: framebuffer: provide generic get_fb_unmapped_area

From: David Herrmann <hidden>
Date: 2014-03-17 12:15:04

Hi

On Mon, Feb 3, 2014 at 6:14 PM, Uwe Kleine-König
[off-list ref] wrote:

quoted hunk

This patch makes mmapping the simple-framebuffer device work on a no-MMU
ARM target. The code is mostly taken from
arch/blackfin/kernel/sys_bfin.c.

Signed-off-by: Uwe Kleine-König <redacted>
---
Hello,

note this is only tested on this no-MMU machine and I don't know enough
about framebuffers and mm to decide if this patch is sane. Also I'm
a bit unsure about the size check, I just believed Geert that
PAGE_ALIGN(info->fix.smem_len) is the right value to check against.

Best regards
Uwe

 drivers/video/fbmem.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 7309ac704e26..d0ccedafec8c 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c

@@ -1491,6 +1491,22 @@ __releases(&info->lock)
        return 0;
 }

+#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
+#define fb_get_unmapped_area get_fb_unmapped_area
+#else
+unsigned long fb_get_unmapped_area(struct file *filp, unsigned long orig_addr,
+               unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+       struct fb_info * const info = filp->private_data;
+       unsigned long fb_size = PAGE_ALIGN(info->fix.smem_len);
+
+       if (pgoff > fb_size || len > fb_size - pgoff)
+               return -EINVAL;
+
+       return (unsigned long)info->screen_base + pgoff;
+}
+#endif
+

Doesn't this break mmu systems? x86 for instance has no
get_fb_unmapped_area(), therefore f_ops->get_unmapped_area() is NULL
and thus falls back to the generic handler of the task (see
mm/mmap.c). If you replace this with your handler, _every_ mmap() call
with be treated as MAP_FIXED with "info->screen_base + pgoff" as
address. This might work in test-cases on the first mmap() call, but
any further call will fail.

Thanks
David

quoted hunk

 static const struct file_operations fb_fops = {
        .owner =        THIS_MODULE,
        .read =         fb_read,

@@ -1502,9 +1518,7 @@ static const struct file_operations fb_fops = {
        .mmap =         fb_mmap,
        .open =         fb_open,
        .release =      fb_release,
-#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
-       .get_unmapped_area = get_fb_unmapped_area,
-#endif
+       .get_unmapped_area = fb_get_unmapped_area,
 #ifdef CONFIG_FB_DEFERRED_IO
        .fsync =        fb_deferred_io_fsync,
 #endif
--

1.8.5.2

--
To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

`h`	back out one level
`j`	next message in thread
`k`	previous message in thread
`l`	drill in
`Esc`	close help / fold thread tree
`?`	toggle this help