Re: [PATCH 3/3] max3100: adds console support for MAX3100

[christian pellegrin <chripell-VaTbYqLCNhc@public.gmane.org>]

On Mon, Mar 22, 2010 at 2:31 AM, Feng Tang <feng.tang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:
>
> Hi Christian,

Hi,

>
> You'd better not call max3110_sr (which calls spi_sync) here, a console's
> putchar() func may be called in some atomic context.
>

ack, I didn't realize that. Unfortunately this makes reliable use of
MAX3100 as a console near impossible. Some SPI master driver use
workqueues (see the bit banging ones). I don't see any way to yield
CPU to them while somehow wait the output has finished (a busy loop
won't work: perhaps the thread calling the console has a higher
priority than the one doing actual SPI output so the system will
deadlock). The only way out I see is to provide a buffer large enough
for all practical purposes. Will try it in the next version of the
patch.

Thanks.

-- 
Christian Pellegrin, see http://www.evolware.org/chri/
"Real Programmers don't play tennis, or any other sport which requires
you to change clothes. Mountain climbing is OK, and Real Programmers
wear their climbing boots to work in case a mountain should suddenly
spring up in the middle of the computer room."

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