RE: [PATCH] mtd: m25p80: consider max message size when use the spi_mem_xx() API

[David Laight]

From: Chuanhua Han
> Sent: 20 August 2018 13:44
> 
> Signed-off-by: Chuanhua Han <chuanhua.han@xxxxxxx>
> ---
> Changes in v3:
>     Rename variable name "val" to "opcode_addr_dummy_sum".
>     Place the legitimacy of the transfer size(i.e., "pi_max_message_size(mem->spi)" and
> "opcode_addr_dummy_sum") into "if (! ctlr - > mem_ops | |! ctlr-> mem_ops->exec_op) {"
> structure and add "spi_max_transfer_size(mem->spi) and opcode_addr_dummy_sum".
>     Adjust the formatting alignment of your code.
>     "(unsigned long)op->data.nbytes" was modified to "(unsigned long)(op->data.nbytes)".
> 
> Fixes: c36ff266dc82 ("spi: Extend the core to ease integration of SPI memory controllers")
> ---
>  drivers/spi/spi-mem.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 990770d..5ec2bc9 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -328,10 +328,24 @@ EXPORT_SYMBOL_GPL(spi_mem_exec_op);
>  int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
>  {
>  	struct spi_controller *ctlr = mem->spi->controller;
> +	unsigned long opcode_addr_dummy_sum = sizeof(op->cmd.opcode) +
> +					      op->addr.nbytes +
> +					      op->dummy.nbytes;

I'd split that (and shorten the variable name) to avoid line wrap. Maybe:

	unsigned long len;

	len = sizeof(op->cmd.opcode) + op->addr.nbytes + op->dummy.nbytes;
> 
>  	if (ctlr->mem_ops && ctlr->mem_ops->adjust_op_size)
>  		return ctlr->mem_ops->adjust_op_size(mem, op);
> 
> +	if (!ctlr->mem_ops || !ctlr->mem_ops->exec_op) {
> +		if (spi_max_message_size(mem->spi) < opcode_addr_dummy_sum ||
> +		    spi_max_transfer_size(mem->spi) < opcode_addr_dummy_sum)
> +			return -EINVAL;

Those comparisons are lexically backwards, you want 'value op constant'.
So:
		if (len > spi_max_message_size(mem->spi) ||
		    len > spi_max_transfer_size(mem->spi))
			return -EINVAL.
Although I'm surprised you need to do both comparisons.

> +
> +		op->data.nbytes = min3((unsigned long)(op->data.nbytes),
> +				       spi_max_transfer_size(mem->spi),
> +				       spi_max_message_size(mem->spi) -
> +				       opcode_addr_dummy_sum);

That looks like a strange limit...

> +	}
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(spi_mem_adjust_op_size);
> --
> 2.7.4

	David

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