re: video, sm501: add OF binding to support SM501

re: video, sm501: add OF binding to support SM501

[Dan Carpenter]

Hello Heiko Schocher,

The patch 4295f9bf74a8: "video, sm501: add OF binding to support
SM501" from Jan 26, 2011, leads to the following static checker
warning:

	drivers/video/fbdev/sm501fb.c:1958 sm501fb_probe()
	warn: strcpy() 'cp' of unknown size might be too large for 'fb_mode'

drivers/video/fbdev/sm501fb.c
    46  static char *fb_mode = "640x480-16@60";

	[ snip ]

  1953                  info->pdata = &sm501fb_def_pdata;
  1954                  if (np) {
  1955                          /* Get EDID */
  1956                          cp = of_get_property(np, "mode", &len);
  1957                          if (cp)
  1958                                  strcpy(fb_mode, cp);

I don't know anything about this hardware but there might be a mode
longer than "640x480-16@60"?

  1959                          prop = of_get_property(np, "edid", &len);
  1960                          if (prop && len = EDID_LENGTH) {

regards,
dan carpenter

Re: video, sm501: add OF binding to support SM501

[Heiko Schocher]

Hello Dan,

Am 10.06.2015 17:51, schrieb Dan Carpenter:
> Hello Heiko Schocher,
>
> The patch 4295f9bf74a8: "video, sm501: add OF binding to support
> SM501" from Jan 26, 2011, leads to the following static checker
> warning:
>
> 	drivers/video/fbdev/sm501fb.c:1958 sm501fb_probe()
> 	warn: strcpy() 'cp' of unknown size might be too large for 'fb_mode'
>
> drivers/video/fbdev/sm501fb.c
>      46  static char *fb_mode = "640x480-16@60";
>
> 	[ snip ]
>
>    1953                  info->pdata = &sm501fb_def_pdata;
>    1954                  if (np) {
>    1955                          /* Get EDID */
>    1956                          cp = of_get_property(np, "mode", &len);
>    1957                          if (cp)
>    1958                                  strcpy(fb_mode, cp);
>
> I don't know anything about this hardware but there might be a mode
> longer than "640x480-16@60"?

Hmm... I just used it with this resolution, but you are right, the
datasheet says "200 MHz DAC support 1280×1024 resolution" ... so, in
this case fb_mode would be to short ... I propose such a fix:

$ git diff
diff --git a/drivers/video/fbdev/sm501fb.c b/drivers/video/fbdev/sm501fb.c
index 9e74e8f..2e57f2e 100644
--- a/drivers/video/fbdev/sm501fb.c
+++ b/drivers/video/fbdev/sm501fb.c
@@ -43,7 +43,9 @@

  #include "edid.h"

-static char *fb_mode = "640x480-16@60";
+static char *fb_default_mode = "640x480-16@60";
+static char fb_mode[20];
+static char *fb_mode_cmdline;
  static unsigned long default_bpp = 16;

  static struct fb_videomode sm501_default_mode = {
@@ -1963,6 +1965,11 @@ static int sm501fb_probe(struct platform_device *pdev)
                                 if (info->edid_data)
                                         found = 1;
                         }
+               } else {
+                       if (fb_mode_cmdline)
+                               strcpy(fb_mode, fb_mode_cmdline);
+                       else
+                               strcpy(fb_mode, fb_default_mode);
                 }
  #endif
                 if (!found) {
@@ -2230,7 +2237,7 @@ static struct platform_driver sm501fb_driver = {

  module_platform_driver(sm501fb_driver);

-module_param_named(mode, fb_mode, charp, 0);
+module_param_named(mode, fb_mode_cmdline, charp, 0);
  MODULE_PARM_DESC(mode,
         "Specify resolution as \"<xres>x<yres>[-<bpp>][@<refresh>]\" ");
  module_param_named(bpp, default_bpp, ulong, 0);

What do you think? If this is OK from your side, I can post this patch
"officially" ...

bye,
Heiko
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

Re: video, sm501: add OF binding to support SM501

[Dan Carpenter]

On Thu, Jun 11, 2015 at 11:24:41AM +0200, Heiko Schocher wrote:
>  static struct fb_videomode sm501_default_mode = {
> @@ -1963,6 +1965,11 @@ static int sm501fb_probe(struct platform_device *pdev)
>                                 if (info->edid_data)
>                                         found = 1;
>                         }
> +               } else {
> +                       if (fb_mode_cmdline)
> +                               strcpy(fb_mode, fb_mode_cmdline);

Could you make this a strncpy()?  These days strlcpy() is
unfashionable...  It's sort of pedantic and it goes over the 80 char
limit but the my static checker will complain if we don't.

				strncpy(fb_mod, fb_mode_cmdline,
					sizeof(fb_mod) - 1);

> +                       else
> +                               strcpy(fb_mode, fb_default_mode);

regards,
dan carpenter