On Wed, 27 Nov 2019, Daniel Vetter <dan...@ffwll.ch> wrote:
> On Wed, Nov 27, 2019 at 07:17:41PM +0100, Daniel Vetter wrote:
>> On Wed, Nov 27, 2019 at 06:31:57PM +0200, Jani Nikula wrote:
>> > Modifying fb_ops directly to override fb_mmap with fb_deferred_io_mmap
>> > and then resetting it to NULL afterwards causes problems all over the
>> > place. First, it prevents making the fbops member of struct fb_info a
>> > const pointer, which means we can't make struct fb_ops const
>> > anywhere. Second, a few places have to go out of their way to restore
>> > the original fb_mmap pointer that gets reset to NULL.
>> >
>> > Preserve the passed in fb_ops by making a copy of it and modifying that
>> > instead. Add a deferred_io_private member to struct fb_info to store the
>> > pointer to the old fb_ops, and restore that at cleanup.
>> >
>> > Cc: Jaya Kumar <jay...@intworks.biz>
>> > Cc: linux-fb...@vger.kernel.org
>> > Signed-off-by: Jani Nikula <jani.nik...@intel.com>
>> >
>> > ---
>> >
>> > Note: If the approach is acceptable, we'll also need to handle the error
>> > returns on memory allocation failures at fb_deferred_io_init() call
>> > sites. There are 13.
>>
>> it's fbdev defio, I think we can do worse with less effort. Just embed a
>> copy of fb_ops into fb_info, and use that, and tada! no memory allocation
>> needed :-)
>>
>> I'd totally r-b that patch.
>>
>> Or do what Ville suggested, add an fb_info->fbdefio.enabled, set that in
>> the _init function and in fb_mmap call fb_deferred_io_mmap for that case
>> instead of the driver's fb_ops->fb_mmap. There's only one caller of that
>> in the entire tree, in fbmem.c. Also, we could/should nuke the
>> EXPORT_SYMBOL(fb_deferred_io_mmap) I think.
>
> I just realized that fb_info->fbdefio is a pointer, so this would be
> really simple to pull off I think.
Heh, having a
int (*fb_deferred_io_mmap)(struct fb_info *, struct vm_area_struct *);
member in struct fb_info, and using that in fbmem.c if non-NULL, was
actually my first idea. I didn't think it was particularly pretty, but
if we don't care about aesthetics...
Would you like that instead of the patch at hand?
BR,
Jani.
> -Daniel
>
>>
>> That version would also get my r-b stamp. So up to you what you prefer.
>> -Daniel
>>
>> > ---
>> > drivers/video/fbdev/core/fb_defio.c | 25 ++++++++++++++++++++++---
>> > include/linux/fb.h | 3 ++-
>> > 2 files changed, 24 insertions(+), 4 deletions(-)
>> >
>> > diff --git a/drivers/video/fbdev/core/fb_defio.c
>> > b/drivers/video/fbdev/core/fb_defio.c
>> > index 82c20c6047b0..36697844c1e0 100644
>> > --- a/drivers/video/fbdev/core/fb_defio.c
>> > +++ b/drivers/video/fbdev/core/fb_defio.c
>> > @@ -200,13 +200,23 @@ static void fb_deferred_io_work(struct work_struct
>> > *work)
>> > mutex_unlock(&fbdefio->lock);
>> > }
>> >
>> > -void fb_deferred_io_init(struct fb_info *info)
>> > +int fb_deferred_io_init(struct fb_info *info)
>> > {
>> > struct fb_deferred_io *fbdefio = info->fbdefio;
>> > + struct fb_ops *fbops;
>> >
>> > BUG_ON(!fbdefio);
>> > +
>> > + fbops = kmemdup(info->fbops, sizeof(*fbops), GFP_KERNEL);
>> > + if (!fbops)
>> > + return -ENOMEM;
>> > +
>> > + fbops->fb_mmap = fb_deferred_io_mmap;
>> > + info->deferred_io_private = info->fbops;
>> > + info->fbops = fbops;
>> > +
>> > mutex_init(&fbdefio->lock);
>> > - info->fbops->fb_mmap = fb_deferred_io_mmap;
>> > +
>> > INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
>> > INIT_LIST_HEAD(&fbdefio->pagelist);
>> > if (fbdefio->delay == 0) /* set a default of 1 s */
>> > @@ -229,6 +239,12 @@ void fb_deferred_io_cleanup(struct fb_info *info)
>> > int i;
>> >
>> > BUG_ON(!fbdefio);
>> > +
>> > + /* sanity check against misuse */
>> > + if (WARN_ON(!info->deferred_io_private ||
>> > + info->fbops->fb_mmap != fb_deferred_io_mmap))
>> > + return;
>> > +
>> > cancel_delayed_work_sync(&info->deferred_work);
>> >
>> > /* clear out the mapping that we setup */
>> > @@ -237,7 +253,10 @@ void fb_deferred_io_cleanup(struct fb_info *info)
>> > page->mapping = NULL;
>> > }
>> >
>> > - info->fbops->fb_mmap = NULL;
>> > + kfree(info->fbops);
>> > + info->fbops = info->deferred_io_private;
>> > + info->deferred_io_private = NULL;
>> > +
>> > mutex_destroy(&fbdefio->lock);
>> > }
>> > EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
>> > diff --git a/include/linux/fb.h b/include/linux/fb.h
>> > index a6ad528990de..65f2abd47745 100644
>> > --- a/include/linux/fb.h
>> > +++ b/include/linux/fb.h
>> > @@ -470,6 +470,7 @@ struct fb_info {
>> > #ifdef CONFIG_FB_DEFERRED_IO
>> > struct delayed_work deferred_work;
>> > struct fb_deferred_io *fbdefio;
>> > + void *deferred_io_private;
>> > #endif
>> >
>> > struct fb_ops *fbops;
>> > @@ -658,7 +659,7 @@ static inline void __fb_pad_aligned_buffer(u8 *dst,
>> > u32 d_pitch,
>> >
>> > /* drivers/video/fb_defio.c */
>> > int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma);
>> > -extern void fb_deferred_io_init(struct fb_info *info);
>> > +extern int fb_deferred_io_init(struct fb_info *info);
>> > extern void fb_deferred_io_open(struct fb_info *info,
>> > struct inode *inode,
>> > struct file *file);
>> > --
>> > 2.20.1
>> >
>> > _______________________________________________
>> > Intel-gfx mailing list
>> > intel-...@lists.freedesktop.org
>> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch
--
Jani Nikula, Intel Open Source Graphics Center
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