Re: [PATCH] vga16fb: refuse to load in face of other driver
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From: Andrew Morton <akpm@linux-foundation.org>
Date: 2010-07-23 00:21:17
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On Tue, 20 Jul 2010 21:19:23 +0200 Marcin Slusarz [off-list ref] wrote:
quoted hunk ↗ jump to hunk
We don't want vga16fb to mess with hardware initialized by other driver. Detect it and refuse to load. It fixes nouveau interrupt storm on some machines. Signed-off-by: Marcin Slusarz <redacted> --- drivers/video/vga16fb.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-)diff --git a/drivers/video/vga16fb.c b/drivers/video/vga16fb.c index 28ccab4..4505446 100644 --- a/drivers/video/vga16fb.c +++ b/drivers/video/vga16fb.c@@ -22,6 +22,7 @@ #include <linux/platform_device.h> #include <linux/screen_info.h> +#include <asm/fb.h> #include <asm/io.h> #include <video/vga.h>@@ -1415,7 +1416,7 @@ static struct platform_device *vga16fb_device; static int __init vga16fb_init(void) { - int ret; + int ret, i; #ifndef MODULE char *option = NULL;@@ -1424,6 +1425,16 @@ static int __init vga16fb_init(void) vga16fb_setup(option); #endif + for (i = 0 ; i < FB_MAX; i++) { + if (!registered_fb[i]) + continue; + if (fb_is_primary_device(registered_fb[i])) { + printk(KERN_INFO "vga16fb: %s is driving the primary card, refusing to load\n", + registered_fb[i]->fix.id); + return -EBUSY; + } + } + ret = platform_driver_register(&vga16fb_driver); if (!ret) {
This seems pretty hacky, and specific to vga16fb. Is vga16fb.c the only fbdev driver (now and forever more) which can grab the hardware from under a different driver's feet? This is the basic and very common problem of two drivers diddling the same hardware, yes? A common way of preventing such collisions is to perform a suitably-checked request_region() in both drivers. Whichever driver gets there second will get a failure and will bale out cleanly. Can that mechanism be made to work in this case?