[PATCH 2/7] fbdev: Make fb_find_mode() return failure if modular

[PATCH 2/7] fbdev: Make fb_find_mode() return failure if modular

[Antonino A. Daplas]

A few drivers call fb_find_mode() even if compiled as a module.  If the
modedb parameter is NULL, the function will use default modedb array which
is marked __init. This will cause a crash.  To avoid this, check if the
driver is compiled as a module, and if it is, fail.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
---

 modedb.c |    4 ++++
 1 files changed, 4 insertions(+)

diff -Nru a/drivers/video/modedb.c b/drivers/video/modedb.c
--- a/drivers/video/modedb.c	2005-02-17 19:29:47 +08:00
+++ b/drivers/video/modedb.c	2005-02-15 22:54:57 +08:00
@@ -474,11 +474,15 @@
 {
     int i;
 
+    if (!db && (info->flags & FBINFO_MODULE))
+	return 0;
+
     /* Set up defaults */
     if (!db) {
 	db = modedb;
 	dbsize = sizeof(modedb)/sizeof(*modedb);
     }
+
     if (!default_mode)
 	default_mode = &modedb[DEFAULT_MODEDB_INDEX];
     if (!default_bpp)




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Re: [PATCH 2/7] fbdev: Make fb_find_mode() return failure if modular

[David Vrabel]

Antonino A. Daplas wrote:
> A few drivers call fb_find_mode() even if compiled as a module.  If the
> modedb parameter is NULL, the function will use default modedb array which
> is marked __init. This will cause a crash.  To avoid this, check if the
> driver is compiled as a module, and if it is, fail.

Why limit the default mode DB to built-in drivers only?

David Vrabel
-- 
David Vrabel, Design Engineer

Arcom, Clifton Road           Tel: +44 (0)1223 411200 ext. 3233
Cambridge CB1 7EA, UK         Web: http://www.arcom.com/


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Re: [PATCH 2/7] fbdev: Make fb_find_mode() return failure if modular

[Antonino A. Daplas]

On Thursday 17 February 2005 22:29, David Vrabel wrote:
> Antonino A. Daplas wrote:
> > A few drivers call fb_find_mode() even if compiled as a module.  If the
> > modedb parameter is NULL, the function will use default modedb array
> > which is marked __init. This will cause a crash.  To avoid this, check if
> > the driver is compiled as a module, and if it is, fail.
>
> Why limit the default mode DB to built-in drivers only?

The default db is used by drivers only once.  After that, it just consumes
memory.

Tony




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Re: [PATCH 2/7] fbdev: Make fb_find_mode() return failure if modular

[James Simmons]

> On Thursday 17 February 2005 22:29, David Vrabel wrote:
> > Antonino A. Daplas wrote:
> > > A few drivers call fb_find_mode() even if compiled as a module.  If the
> > > modedb parameter is NULL, the function will use default modedb array
> > > which is marked __init. This will cause a crash.  To avoid this, check if
> > > the driver is compiled as a module, and if it is, fail.
> >
> > Why limit the default mode DB to built-in drivers only?
> 
> The default db is used by drivers only once.  After that, it just consumes
> memory.

For modules it wouldn't be that hard to add the modedb from userland after 
loading. First insmod your module. Normally modular fbdev driver don't set 
the hardware explictly. Once we have sysfs it will be easy. Next send the 
new modes to the db. Next select the mode you want. 


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Re: [PATCH 2/7] fbdev: Make fb_find_mode() return failure if modular

[Antonino A. Daplas]

On Friday 18 February 2005 06:09, James Simmons wrote:
> > On Thursday 17 February 2005 22:29, David Vrabel wrote:
> > > Antonino A. Daplas wrote:
> > > > A few drivers call fb_find_mode() even if compiled as a module.  If
> > > > the modedb parameter is NULL, the function will use default modedb
> > > > array which is marked __init. This will cause a crash.  To avoid
> > > > this, check if the driver is compiled as a module, and if it is,
> > > > fail.
> > >
> > > Why limit the default mode DB to built-in drivers only?
> >
> > The default db is used by drivers only once.  After that, it just
> > consumes memory.
>
> For modules it wouldn't be that hard to add the modedb from userland after
> loading. First insmod your module. Normally modular fbdev driver don't set
> the hardware explictly. Once we have sysfs it will be easy. Next send the
> new modes to the db. Next select the mode you want.
>

Yes, also, modedb contains modes from different displays most of which
are unusable.  If you want, you can create a private mode database for your
driver. See how rivafb, savagefb and radeonfb do it.  In fact, all drivers
already have a private modelist, but if not explicitly created, will contain
only one entry, coming from info->var.  Each time you use fbset, the 
mode is automatically added to the modelist.

Tony




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