linux-kernel - Re: [PATCH 3/4] usb_debug,usb_generic_serial: implement sysrq and serial break

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Date:	Tue, 12 May 2009 10:02:17 -0700
From:	Greg KH <greg@...ah.com>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	stern@...land.harvard.edu, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] usb_debug,usb_generic_serial: implement sysrq and
	serial break

On Mon, May 11, 2009 at 03:24:09PM -0500, Jason Wessel wrote:
> The usb_debug driver was modified to implement serial break handling
> by using a "magic" data packet comprised of the sequence:
> 
>        0x00 0xff 0x01 0xfe   0x00 0xfe 0x01 0xff
> 
> When the tty layer requests a serial break the usb_debug driver sends
> the magic packet.  On the receiving side the magic packet is thrown
> away or a sysrq is activated depending on what kernel .config options
> have been set.
> 
> The generic serial driver was modified as well as the usb serial
> headers to generically implement sysrq processing in the same way the
> non usb uart based drivers implement the sysrq handling.  This will
> allow other usb serial devices to implement sysrq handling as desired.
> 
> The new usb serial functions are named similarly and implemented
> similarly to the uart functions as follows:
> 
> usb_serial_handle_break <-> uart_handle_break
> usb_serial_handle_sysrq_char <-> uart_handle_sysrq_char
> 
> Signed-off-by: Jason Wessel <jason.wessel@...driver.com>
> ---
>  drivers/usb/serial/Kconfig     |    7 +++++++
>  drivers/usb/serial/generic.c   |   30 ++++++++++++++++++------------
>  drivers/usb/serial/usb_debug.c |   39 +++++++++++++++++++++++++++++++++++++++
>  include/linux/usb/serial.h     |   34 ++++++++++++++++++++++++++++++++--
>  4 files changed, 96 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
> index c480ea4..3229321 100644
> --- a/drivers/usb/serial/Kconfig
> +++ b/drivers/usb/serial/Kconfig
> @@ -42,6 +42,13 @@ config USB_SERIAL_CONSOLE
>  
>  	  If unsure, say N.
>  
> +config USB_SERIAL_SYSRQ
> +       bool "Support inbound sysrq"
> +       depends on USB_SERIAL_CONSOLE && MAGIC_SYSRQ
> +       help
> +         Say y here to enable support for sysrq if the usb serial
> +         driver implements support for sysrq.
> +

I took this Kconfig option out, as it would just be confusing.  Just
always enable this, and if a driver wants to support it, it can, no need
for ifdefs or anything else.

thanks,

greg k-h
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