linux-kernel - Re: [PATCH] Provide better abstraction for the serial drivers to xmit buf and tty

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Date:	Wed, 18 Apr 2007 20:12:05 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Corey Minyard <minyard@....org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH] Provide better abstraction for the serial drivers to
 xmit buf and tty

> Currently the uart_info structure is allocated on an open, so it's not
> available until that point in time.  The trouble is that console_init() is
> called before memory is set up, so you can't allocate the uart_info
> until it's too late for the console or a debugger that wants to work
> early, though it's ok for IPMI.

A debugger can provide a pre-existing uart_info and buffer. The
initialisation is only done if the uart_state->info pointer is NULL.

> The uart_info struct is not very big, maybe it would be best to pull that
> into uart_port?  But the circ buffer might still be a problem, since it
> would need to be dynamically allocated and it might need to be
> checked instead.

How about this (untested idea in the finest Linux tradition)

Add

uart_console_prepare(struct uart_port *port, struct uart_info
*info, void *buffer)
{
	port->info = info;
	info->xmit.buf = buffer;
	... etc ...
	info->flags |= UPF_BOOTALLOCATED;
}


in uart_shutdown() check UPF_BOOTALLOCATED and don't free xmit.buf if so.

ditto in uart_remove_one_port for info itself


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