Re: [PATCH 1/3 v3]spi: controller driver for Designware SPI core

[Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>]

On Mon, 12 Oct 2009 14:19:15 +0800
Feng Tang <feng.tang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:

> >From 2945f4eab344742d878ea10a774285fe770e6b10 Mon Sep 17 00:00:00 2001
> From: Feng Tang <feng.tang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Date: Sat, 10 Oct 2009 14:55:48 +0800
> Subject: [PATCH 1/3] spi: controller driver for Designware SPI core
> 
> Driver for the Designware SPI core, it supports multipul interfaces
> like PCI/APB etc. User can use "dw_apb_ssi_db.pdf" from Synopsys as
> HW datasheet.
> 
> ...
>
> +#define START_STATE	((void *)0)
> +#define RUNNING_STATE	((void *)1)
> +#define DONE_STATE	((void *)2)
> +#define ERROR_STATE	((void *)-1)

What's going on here?

>
> ...
>
> +static void *next_transfer(struct dw_spi *dws)
> +{
> +	struct spi_message *msg = dws->cur_msg;
> +	struct spi_transfer *trans = dws->cur_transfer;
> +
> +	/* Move to next transfer */
> +	if (trans->transfer_list.next != &msg->transfers) {
> +		dws->cur_transfer =
> +			list_entry(trans->transfer_list.next,
> +					struct spi_transfer,
> +					transfer_list);
> +		return RUNNING_STATE;
> +	} else
> +		return DONE_STATE;
> +}

Seems that you only need a single word of device-private storage in
`struct spi_message'.  So instead of kmallocing enough memory to store
the `state' value, you've stuffed that value directly into the
spi_message, pretending to be a kernel address.

Correct?

If so, it's a bit nasty but probabyl a worthwhile thing to do.  It'd be
nice to add a code comment somewhere explaining this.  Plasing it at
the definition site of the *_STATE values would be appropriate.  



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