linux-kernel - Re: [PATCH] serial: pnx8xxx_uart: Fix break signal handling

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Message-ID: <4142f31c0901130522n5273fb67j41cf1aaf7b32853c@mail.gmail.com>
Date:	Tue, 13 Jan 2009 14:22:00 +0100
From:	"Mischa Jonker" <m.d.s.x.jonker@...il.com>
To:	"Alan Cox" <alan@...rguk.ukuu.org.uk>
Cc:	"Jonker M.D.S.X." <nlv14114@...nl-htc01.nxp.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: pnx8xxx_uart: Fix break signal handling

On Tue, Jan 13, 2009 at 1:11 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> On Tue, 13 Jan 2009 12:09:13 +0100
> "Jonker M.D.S.X." <nlv14114@...nl-htc01.nxp.com> wrote:
>
>> From: Mischa Jonker <mischa.jonker@....com>
>>
>> When a break signal is detected, the next character should be ignored.
>> This was not implemented correctly for the pnx8xxx_uart driver.
>>
>> Signed-off-by: Mischa Jonker <mischa.jonker@....com>
>> ---
>>
>> diff --git a/drivers/serial/pnx8xxx_uart.c b/drivers/serial/pnx8xxx_uart.c
>> index 22e30d2..1bb8f1b 100644
>> --- a/drivers/serial/pnx8xxx_uart.c
>> +++ b/drivers/serial/pnx8xxx_uart.c
>> @@ -187,7 +187,7 @@ static void pnx8xxx_rx_chars(struct pnx8xxx_port *sport)
>>       status = FIFO_TO_SM(serial_in(sport, PNX8XXX_FIFO)) |
>>                ISTAT_TO_SM(serial_in(sport, PNX8XXX_ISTAT));
>>       while (status & FIFO_TO_SM(PNX8XXX_UART_FIFO_RXFIFO)) {
>> -             ch = serial_in(sport, PNX8XXX_FIFO);
>> +             ch = serial_in(sport, PNX8XXX_FIFO) & 0xff;
>
> This appears to be unrelated.
>

Correct, you can look to it as two separate bugs:
a) the next character is not ignored while it should;
b) the status bits 31-8 are copied to the 'ch' variable while they shouldn't.

Both bugs prevent correct break signal handling (and therefore correct
behaviour of the magic SysRq key). Bug b didn't cause too much trouble
earlier because in most situations the status bits are all zero; for
this case they unfortunately aren't.

I can split them up if you like, or we can keep them together, as they
are in fact related.

Thanks,

Mischa Jonker
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