[PATCH] interrupt driven hvc_console as vio device (final)
From: Ryan Arnold (rsa_at_us.ibm.com)
Date: 08/27/04
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To: Kernel Mailing List <linux-kernel@vger.kernel.org> Date: Fri, 27 Aug 2004 04:40:44 -0500
Andrew,
Here is the revised hvc_console patch which fixes the issues you were
concerned with in the previous patch. Your two concerns were:
1. Yielding in hvc_close(). This was replaced with
tty_wait_until_sent() which seem to be built for this exact scenario. I
also restructured hvc_close() to be more elegant and less confusing than
in the previous patch.
2. Spinlocks in hvc_chars_in_buffer() and hvc_write_room() which simply
protected values read from hvc_struct instances. I removed the
spinlocks and didn't put in memory barriers because they really weren't
needed.
Paul MacKerras approved the architecture portions of the previous
incarnation of this patch and I have touched the arch code in this
revision. Ben Herrenschmidt, who contributed a portion of the orignal
code this patch was based on has signed off on this patch.
Changelog:
This is an hvc_console patch which provides driver and ppc64
architecture fixes to enable the hvc_console driver to register itself
as a vio device with the vio bus, provide hotplug add/remove for vty
adapters, and act as an interrupt driven driver on Power-5 hardware or
remain as a polling driver on Power-4 hardware.
arch/ppc64/kernel/hvconsole.c
-----------------------------------------------------------------------
-Changed hvc_get_chars() and hvc_put_chars() api to take vtermno rather
than index number.
-Added hvc_find_vtys() function which walks the bus looking for
vterm/vty devices to callback to the hvc_console driver. This provides
console output functionality prior to early console init (pre mem init
and pre device probe).
include/asm-ppc64/hvconsole.h
-----------------------------------------------------------------------
-Changed hvc_get_chars() and hvc_put_chars() api to take vtermno rather
than index number.
-Added hvc_find_vtys() function.
-Added hvc_instantiate() function which is implemented by a console
driver wanting to receive a callback of and early console init.
drivers/char/hvc_console.c
-----------------------------------------------------------------------
-Switch khvcd from kernel_threads to kthreads which got rid of
deprecated daemonize().
-Added module exit clause to be thorough (not terribly necessary with a
console driver of course)
-Added early discovery of vterm/vty adapters by doing a bus walk on
early console init which results in hvc_instantiate() callback and
addition of the vtermno into a static array of vtermnos supported as
console adapters (meaning the console api's work against these vtermnos
prior to full console initialization).
-This driver is now registered as a vio driver which means that vty
adapters are now managed via probe/remove. This means hvc_console
supports hotplug vty adapters.
-Driver now requests more device nodes than what was found on the
initial bus walk when registered as a tty driver to make room for
hotplug vty adapters. These secondary vty adapters provide a tty tunnel
between partitions.
-Removed static hvc_struct array and replaced with a linux list that has
elements (hvc_struct instances) added/removed on probe/remove AFTER
early console init. This is important because kmalloc can't be done at
early console init.
-Driver now either runs in interrupt driven mode or in polling mode on
older hardware. The khvcd is smart enough to not 'schedule()' when
there are no interrupts.
-kobjects are now used for ref counting on the hvc_struct instances.
-This driver puts the tty layer to sleep on hvc_close() if there are
pending data writes being blocked by firmware.
-Removed useless spinlocks in hvc_chars_in_buffer() and hvc_write_room.
Thanks,
Ryan S. Arnold
IBM Linux Technology Center
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- Previous message: Anton Altaparmakov: "Re: Termination of the Philips Webcam Driver (pwc)"
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