From: Timur Tabi <timur@freescale.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: gregkh <gregkh@suse.de>, lkml <linux-kernel@vger.kernel.org>
Subject: Re: Writing a console/tty driver -- how to use tty_port?
Date: Thu, 28 Oct 2010 16:08:22 -0500 [thread overview]
Message-ID: <4CC9E646.6070405@freescale.com> (raw)
In-Reply-To: <201010282257.33898.arnd@arndb.de>
Arnd Bergmann wrote:
> If the device is not a UART, the best option may be to make the driver
> a backend to the hvc driver, like e.g. drivers/char/hvc_tile.c.
The current version *is* a backend to hvc, but I have to abandon that because of
this thread:
http://lists.ozlabs.org/pipermail/linuxppc-dev/2010-September/085664.html
I posted a patch that causes hvc to spin if the backend driver returns -EAGAIN,
which is my driver does when the output buffer is full.
In other words, hvc does not support backend drivers that can detect full output
buffers.
> This works for all devices with or without interrupts that don't need
> to set up the communication parameters but simply provide a read/write
> character interface.
If my patch were accepted, I wouldn't need to do the rewrite. Dropping
characters during a printk() is not acceptable for us.
--
Timur Tabi
Linux kernel developer at Freescale
next prev parent reply other threads:[~2010-10-28 21:08 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-27 21:04 Writing a console/tty driver -- how to use tty_port? Timur Tabi
2010-10-27 22:19 ` Alan Cox
2010-10-28 19:35 ` Timur Tabi
2010-10-29 13:55 ` Timur Tabi
2010-10-29 14:14 ` Timur Tabi
2010-10-28 20:34 ` Timur Tabi
2010-10-28 20:47 ` Timur Tabi
2010-10-28 20:57 ` Arnd Bergmann
2010-10-28 21:08 ` Timur Tabi [this message]
2010-10-29 14:21 ` Arnd Bergmann
2010-10-28 22:11 ` Alan Cox
2010-10-29 23:55 ` Arnd Bergmann
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