linux-kernel - Re: [PATCH] n_gsm: Fix write handling for zero bytes written

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Message-ID: <ea5e0639-4419-c60b-059a-8fbd057fc6e3@kernel.org>
Date:   Tue, 18 Aug 2020 12:14:49 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH] n_gsm: Fix write handling for zero bytes written

On 18. 08. 20, 11:56, Tony Lindgren wrote:
> Hi,
> 
> * Jiri Slaby <jirislaby@...nel.org> [200818 08:24]:
>> On 17. 08. 20, 15:54, Tony Lindgren wrote:
>>> If write returns zero we currently end up removing the message
>>> from the queue. Instead of removing the message, we want to just
>>> break out of the loop just like we already do for error codes.
>>
>> When exactly does the only writer (gsmld_output) return zero for
>> non-zero len parameter?
> 
> I ran into this when testing with the WIP serial core PM runtime
> changes from Andy Shevchenko earlier. If there are also other
> cases where we have serial drivers return 0, I don't know about
> them.

Sorry, I don't understand: my gsmld_output() ignores the return value
from drivers' write and returns something greater than zero or a
negative error. What tree/SHA do you run?

> Basically with the WIP serial core changes, if the open serial port
> is in PM runtime suspended state with it's autosuspend_delay_ms
> expired, we have write return 0 and just wake up the serial device
> on TX.


-- 
js