Re: [PATCH 4/5] tpm_tis_spi: Remove limitation of transfers to MAX_SPI_FRAMESIZE bytes

Jarkko Sakkinen
2017-02-24T11:56:15Z

On Thu, Feb 16, 2017 at 04:08:25PM +0000, Peter Huewe wrote:
> Limiting transfers to MAX_SPI_FRAMESIZE was not expected by the upper
> layers, as tpm_tis has no such limitation. Add a loop to hide that
> limitation.
>
> Cc: <stable@vger.kernel.org>
> Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy")
> Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
> Signed-off-by: Peter Huewe <peter.huewe@infineon.com>
> ---
> drivers/char/tpm/tpm_tis_spi.c | 108 ++++++++++++++++++++++-------------------
> 1 file changed, 57 insertions(+), 51 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> index 16938e2253d2..b50c5b072df3 100644
> --- a/drivers/char/tpm/tpm_tis_spi.c
> +++ b/drivers/char/tpm/tpm_tis_spi.c
> @@ -61,68 +61,74 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u8 len,
> {
> struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
> int ret;
> - struct spi_message m;
> - struct spi_transfer spi_xfer = {
> - .tx_buf = phy->tx_buf,
> - .rx_buf = phy->rx_buf,
> - .len = 4,
> - .cs_change = 1,
> - };
> -
> - if (len > MAX_SPI_FRAMESIZE)
> - return -ENOMEM;
>
> - phy->tx_buf[0] = direction | (len - 1);
> - phy->tx_buf[1] = 0xd4;
> - phy->tx_buf[2] = addr >> 8;
> - phy->tx_buf[3] = addr;
> + spi_bus_lock(phy->spi_device->master);
>
> - spi_message_init(&m);
> - spi_message_add_tail(&spi_xfer, &m);
> + while (len) {
> + struct spi_message m;
> + struct spi_transfer spi_xfer = {
> + .tx_buf = phy->tx_buf,
> + .rx_buf = phy->rx_buf,
> + .len = 4,
> + .cs_change = 1,
> + };

I like the habbit of keeping all the declarations in the beginning of
the function as we mostly have in the subsystem. It gives a fast view
what the function eats and how much stack it uses.

If you really think that declaring spi_xfer here is a good idea please
create a separate "helper" function for it.

/Jarkko