From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Ruder <andy@aeruder.net>
Date: Thu, 10 Apr 2014 13:57:59 -0500
Subject: [U-Boot] [PATCH RESEND-WITH-JUSTIFICATION] spi: soft_spi:
 Support NULL din/dout buffers
In-Reply-To: <CAD6G_RQYupvndgohh-dR93PM-7Q-RoPjhCLYuHr9rSxiAbZm5A@mail.gmail.com>
References: <1397146782-28966-1-git-send-email-andrew.ruder@elecsyscorp.com>
	<CAD6G_RQYupvndgohh-dR93PM-7Q-RoPjhCLYuHr9rSxiAbZm5A@mail.gmail.com>
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On Fri, Apr 11, 2014 at 12:24:20AM +0530, Jagan Teki wrote:
> At-least from zynq_spi.c case - I wouldn't find that obscure case as you pointed
> and even with dout NULL which is status poll from (sf_ops.c).

zynq_spi is correct, soft_spi is not.

zynq_spi.c:
int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
		void *din, unsigned long flags)
{
	const u8 *tx_buf = dout;
	u8 *rx_buf = din, buf;
			[...]
			if (tx_buf)
				buf = *tx_buf++;
			else
				buf = 0;
			[...]
			if (rx_buf)
				*rx_buf++ = buf;
			[...]

> It would be great if you mentioned issue scenario for status poll case
> drivers/mtd/spi/sf_ops.c:               ret = spi_xfer(spi, 8, NULL,
> &status, 0);

That breaks on soft_spi, hence the patch.

Cheers,
Andy