On Mon, Apr 14, 2025 at 04:56:53PM +0200, Stefano Garzarella wrote:
> From: Stefano Garzarella <sgarz...@redhat.com>
>
> This driver does not support interrupts, and receiving the response is
> synchronous with sending the command.
>
> So we can set TPM_CHIP_FLAG_SYNC to support synchronous send() and
> return responses in the same buffer used for commands. This way we
> don't need to implement recv() op.
>
> Keep using the same pre-allocated buffer to avoid having to allocate
> it for each command. We need the buffer to have the header required by
> the SVSM protocol and the command contiguous in memory.
>
> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
Similar comments, and a bit redundancy does not matter i.e., they can
have pretty much the same explanation.
> ---
> drivers/char/tpm/tpm_svsm.c | 27 +++++++++++----------------
> 1 file changed, 11 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_svsm.c b/drivers/char/tpm/tpm_svsm.c
> index d3ca5615b6f7..db1983072345 100644
> --- a/drivers/char/tpm/tpm_svsm.c
> +++ b/drivers/char/tpm/tpm_svsm.c
> @@ -25,38 +25,32 @@ struct tpm_svsm_priv {
> void *buffer;
> };
>
> -static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t len,
> +static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t cmd_len,
> size_t buf_size)
> {
> struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
> int ret;
>
> - ret = svsm_vtpm_cmd_request_fill(priv->buffer, 0, buf, len);
> + ret = svsm_vtpm_cmd_request_fill(priv->buffer, 0, buf, cmd_len);
> if (ret)
> return ret;
>
> /*
> * The SVSM call uses the same buffer for the command and for the
> - * response, so after this call, the buffer will contain the response
> - * that can be used by .recv() op.
> + * response, so after this call, the buffer will contain the response.
> + *
> + * Note: we have to use an internal buffer because the device in SVSM
> + * expects the svsm_vtpm header + data to be physically contiguous.
> */
> - return snp_svsm_vtpm_send_command(priv->buffer);
> -}
> -
> -static int tpm_svsm_recv(struct tpm_chip *chip, u8 *buf, size_t len)
> -{
> - struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
> + ret = snp_svsm_vtpm_send_command(priv->buffer);
> + if (ret)
> + return ret;
>
> - /*
> - * The internal buffer contains the response after we send the command
> - * to SVSM.
> - */
> - return svsm_vtpm_cmd_response_parse(priv->buffer, buf, len);
> + return svsm_vtpm_cmd_response_parse(priv->buffer, buf, buf_size);
> }
>
> static struct tpm_class_ops tpm_chip_ops = {
> .flags = TPM_OPS_AUTO_STARTUP,
> - .recv = tpm_svsm_recv,
> .send = tpm_svsm_send,
> };
>
> @@ -85,6 +79,7 @@ static int __init tpm_svsm_probe(struct platform_device
> *pdev)
>
> dev_set_drvdata(&chip->dev, priv);
>
> + chip->flags |= TPM_CHIP_FLAG_SYNC;
> err = tpm2_probe(chip);
> if (err)
> return err;
> --
> 2.49.0
>
BR, Jarkko
