[PATCH] tpm-dev: Require response to be read only if there actually is a response

[Alexander Steffen]

If the tpm_transmit call in tpm_common_write fails for any reason, there is
no response that could be read. Therefore, do not require the application
to issue a read call before sending further commands. This restores the
behavior from before support for partial reads was introduced.

Signed-off-by: Alexander Steffen <alexander.stef...@infineon.com>
---
Feel free to merge this into Tadeusz' original commit.

 drivers/char/tpm/tpm-dev-common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-dev-common.c 
b/drivers/char/tpm/tpm-dev-common.c
index 344739223451..5eecad233ea1 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -140,7 +140,8 @@ ssize_t tpm_common_write(struct file *file, const char 
__user *buf,
         * tpm_read or a user_read_timer timeout. This also prevents split
         * buffered writes from blocking here.
         */
-       if (!priv->response_read || priv->command_enqueued) {
+       if ((!priv->response_read && priv->response_length) ||
+           priv->command_enqueued) {
                ret = -EBUSY;
                goto out;
        }
-- 
2.17.1