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SubjectRe: Serial 8250: clear the lsr_break_flag at open
Russell King wrote:
>
> The backup code is something I never properly reviewed, so no comments
> there. The tx_empty code I assumed would be a relatively rare event,
> except when closing the port (at which point you don't particularly care
> about errors anyway, not even the break flag since chances are you'll
> miss the following character.)
>
That "if" statement in the backup code does look a little dodgy, more
than is perhaps required. I think it's correct, but I need to add
a lock there in my patch to protect the LSR check.
> Given that people might want to poll it for various reasons, I guess
> saving the status away should be done. However, there's a slight issue
> with working out which character the error is associated with. Careful
> locking may be the answer to that though.
>
I think as long as you hold the port lock while you grab the LSR and
set the saved flags it will work.
> As for start_tx, yes, though slightly harder to check. Maybe the code
> should be modified to reduce the number of potential LSR reads by reading
> the IIR first, and only if that shows no interrupt pending should the LSR
> be read (and the error flags remembered.)
>
The version of start_tx in 2.6.21 does check IIR first, and it only
checks the LSR if UART_BUG_TXEN is set, so I assume that's not
a big deal.

I'll sleep on it tonight, look it over tomorrow morning, and resend the
patch.

Thanks,

-corey
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