On Tue, Apr 08, 2025 at 10:32:06AM +0200, Stefano Garzarella wrote:
> From: Stefano Garzarella <sgarz...@redhat.com>
>
> Some devices do not support interrupts and provide a single synchronous
> operation to send the command and receive the response on the same buffer.
>
> Currently, these types of drivers must use an internal buffer where they
> temporarily store the response between .send() and recv() calls.
>
> Introduce a new flag (TPM_CHIP_FLAG_SYNC) to support synchronous send().
> If that flag is set by the driver, tpm_try_transmit() will use the send()
> callback to send the command and receive the response on the same buffer
> synchronously. In that case send() return the number of bytes of the
> response on success, or -errno on failure.
>
> Suggested-by: Jason Gunthorpe <j...@ziepe.ca>
> Suggested-by: Jarkko Sakkinen <jar...@kernel.org>
> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
> ---
> include/linux/tpm.h | 1 +
> drivers/char/tpm/tpm-interface.c | 18 +++++++++++++++---
> 2 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 2e38edd5838c..0e9746dc9d30 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -350,6 +350,7 @@ enum tpm_chip_flags {
> TPM_CHIP_FLAG_SUSPENDED = BIT(8),
> TPM_CHIP_FLAG_HWRNG_DISABLED = BIT(9),
> TPM_CHIP_FLAG_DISABLE = BIT(10),
> + TPM_CHIP_FLAG_SYNC = BIT(11),
> };
>
> #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
> diff --git a/drivers/char/tpm/tpm-interface.c
> b/drivers/char/tpm/tpm-interface.c
> index 3b6ddcdb4051..9fbe84b5a131 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -114,8 +114,17 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
> void *buf, size_t bufsiz)
> return rc;
> }
>
> - /* A sanity check. send() should just return zero on success e.g.
> - * not the command length.
> + /* Synchronous devices return the response directly during the send()
> + * call in the same buffer.
> + */
Nit:
/*
* ...
It's wrong in the existing comment.
> + if (chip->flags & TPM_CHIP_FLAG_SYNC) {
> + len = rc;
> + rc = 0;
> + goto out_send_sync;
> + }
> +
> + /* A sanity check. send() of asynchronous devices should just return
> + * zero on success e.g. not the command length.
> */
> if (rc > 0) {
> dev_warn(&chip->dev,
> @@ -151,7 +160,10 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
> void *buf, size_t bufsiz)
> if (len < 0) {
> rc = len;
> dev_err(&chip->dev, "tpm_transmit: tpm_recv: error %d\n", rc);
> - } else if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
> + return rc;
> + }
> +out_send_sync:
out_sync would be sufficient
> + if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
> rc = -EFAULT;
>
> return rc ? rc : len;
> --
> 2.49.0
>
BR, Jarkko
