From 04fe47015d7726b42c34615c124697c7a3537bf0 Mon Sep 17 00:00:00 2001 From: Stefano Garzarella Date: Fri, 20 Jun 2025 15:08:08 +0200 Subject: [PATCH] tpm: support devices with synchronous send() 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. Signed-off-by: Stefano Garzarella Suggested-by: Jason Gunthorpe Suggested-by: Jarkko Sakkinen Reviewed-by: Jarkko Sakkinen Signed-off-by: Jarkko Sakkinen --- drivers/char/tpm/tpm-interface.c | 20 +++++++++++++++++--- include/linux/tpm.h | 1 + 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index 816b7c690bc92..512882ac0db17 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -114,8 +114,19 @@ 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. + */ + if (chip->flags & TPM_CHIP_FLAG_SYNC) { + len = rc; + rc = 0; + goto out_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 +162,10 @@ out_recv: 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_sync: + if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length)) rc = -EFAULT; return rc ? rc : len; diff --git a/include/linux/tpm.h b/include/linux/tpm.h index cafe8c283e889..804fbbe3873df 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -351,6 +351,7 @@ 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) -- 2.47.2