Re: [PATCH 6/7] tty/powerpc: introduce the ePAPR embedded hypervisorbyte channel driver

From: Timur Tabi
Date: Thu May 19 2011 - 12:06:14 EST

Alan Cox wrote:
>> > + /* Pass the received data to the tty layer. Note that this
>> > + * function calls tty_buffer_request_room(), so I'm not sure if
>> > + * we should have also called tty_buffer_request_room().
>> > + */
>> > + ret = tty_insert_flip_string(ttys, buffer, len);

> You only need to request_room in advance if you can't handle the case
> where the insert_flip_string returns less than you stuffed down it.

If tty_insert_flip_string() returns less than I stuffed down it, the characters
it didn't accept will be dropped. That's because once I receive them, I have
nowhere else to put them. I suppose I could implement a receive FIFO, but that
seems overkill. If calling tty_buffer_request_room() ensures that
tty_insert_flip_string() always accepts all the characters, I would rather do that.

Timur Tabi
Linux kernel developer at Freescale

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