Messages in this thread | | | Date | Mon, 26 Apr 2010 17:35:16 +0300 | Subject | Re: [PATCH v3] x86: Do not write into VGA memory space if there is no VGA device in the system | From | Pekka Enberg <> |
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On Mon, Apr 26, 2010 at 5:05 PM, Guenter Roeck <guenter.roeck@ericsson.com> wrote: > On Mon, Apr 26, 2010 at 05:36:05AM -0400, Pekka Enberg wrote: >> Guenter Roeck kirjoitti: >> > Ensure that early_printk() does not write into VGA memory space >> > if there is not VGA device in the system. >> > >> > Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com> >> > --- >> > v3: >> > Changes are now limited to early_printk.c. Functionality is retained, meaning >> > there will still be output on the VGA console before setup_early_printk() >> > is called, but only if a VGA device is known to exist in the system. >> > >> > arch/x86/kernel/early_printk.c | 17 +++++++++++++---- >> > 1 files changed, 13 insertions(+), 4 deletions(-) >> > >> > diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c >> > index b9c830c..783cb25 100644 >> > --- a/arch/x86/kernel/early_printk.c >> > +++ b/arch/x86/kernel/early_printk.c >> > @@ -170,10 +170,13 @@ asmlinkage void early_printk(const char *fmt, ...) >> > int n; >> > va_list ap; >> > >> > - va_start(ap, fmt); >> > - n = vscnprintf(buf, sizeof(buf), fmt, ap); >> > - early_console->write(early_console, buf, n); >> > - va_end(ap); >> > + if (early_console && (early_console_initialized || >> > + boot_params.screen_info.orig_video_isVGA == 1)) { >> > + va_start(ap, fmt); >> > + n = vscnprintf(buf, sizeof(buf), fmt, ap); >> > + early_console->write(early_console, buf, n); >> > + va_end(ap); >> > + } >> > } >> > >> > static inline void early_console_register(struct console *con, int keep_early) >> > @@ -233,6 +236,12 @@ static int __init setup_early_printk(char *buf) >> > #endif >> > buf++; >> > } >> > + >> > + /* If there is no VGA device, don't try to use it as early console. */ >> > + if (early_console == &early_vga_console && >> > + boot_params.screen_info.orig_video_isVGA != 1) >> > + early_console = NULL; >> >> Wouldn't it be better to switch to, say, serial console here to avoid >> the NULL check in early_printk()? >> > This would be another possibility. > > However, since the serial console was not explicitly selected, it would possibly > not be initialized. My understanding is that Peter had a problem with that. > > One can argue that it would still be better to select the serial console in that case, > even though it might not be initialized. Actually, most likely it is (if it exists), > since the system must presumably have some means to communicate with the world. > > I am pretty much open to either option, if that results in the patch being accepted. > Just let me know which way to go.
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