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SubjectRe: [PATCH v4 2/2] tpm: add support for nonblocking operation
On Tue, Aug 07, 2018 at 01:27:49PM -0700, Tadeusz Struk wrote:
> Currently the TPM driver only supports blocking calls, which doesn't allow
> asynchronous IO operations to the TPM hardware.
> This patch changes it and adds support for nonblocking write and a new poll
> function to enable applications, which want to take advantage of this.
>
> Tested-by: Philip Tricca <philip.b.tricca@intel.com>
> Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
> ---
> drivers/char/tpm/tpm-dev-common.c | 149 ++++++++++++++++++++++++++++---------
> drivers/char/tpm/tpm-dev.c | 16 +++-
> drivers/char/tpm/tpm-dev.h | 17 +++-
> drivers/char/tpm/tpm-interface.c | 1
> drivers/char/tpm/tpm.h | 1
> drivers/char/tpm/tpmrm-dev.c | 19 +++--
> 6 files changed, 150 insertions(+), 53 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index f0c033b69b62..f71d80b94451 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -17,11 +17,36 @@
> * License.
> *
> */
> +#include <linux/poll.h>
> #include <linux/slab.h>
> #include <linux/uaccess.h>
> +#include <linux/workqueue.h>
> #include "tpm.h"
> #include "tpm-dev.h"
>
> +static struct workqueue_struct *tpm_dev_wq;

A naming contradiction with tpm_common_read() and tpm_common_write(). To
sort that up I would suggest adding a commit to the patch set that
renames these functions as tpm_dev_common_read() and
tpm_dev_common_write() and use the name tpm_common_dev_wq here.

> +static DEFINE_MUTEX(tpm_dev_wq_lock);

This is an unacceptable way to do it, Rather add:

int __init tpm_dev_common_init(void)
{
tpm_dev_common_wq = alloc_workqueue("tpm_dev_wq", WQ_MEM_RECLAIM, 0);
if (!tpm_dev_common_wq)
return -ENOMEM;

return 0;
}

and call this in the driver initialization.

> +
> +static void tpm_async_work(struct work_struct *work)
> +{
> + struct file_priv *priv =
> + container_of(work, struct file_priv, async_work);
> + ssize_t ret;
> +
> + mutex_lock(&priv->buffer_mutex);
> + priv->command_enqueued = false;
> + ret = tpm_transmit(priv->chip, priv->space, priv->data_buffer,
> + sizeof(priv->data_buffer), 0);
> +
> + tpm_put_ops(priv->chip);
> + if (ret > 0) {
> + priv->data_pending = ret;
> + mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
> + }
> + mutex_unlock(&priv->buffer_mutex);
> + wake_up_interruptible(&priv->async_wait);
> +}
> +
> static void user_reader_timeout(struct timer_list *t)
> {
> struct file_priv *priv = from_timer(priv, t, user_read_timer);
> @@ -29,30 +54,44 @@ static void user_reader_timeout(struct timer_list *t)
> pr_warn("TPM user space timeout is deprecated (pid=%d)\n",
> task_tgid_nr(current));
>
> - schedule_work(&priv->work);
> + schedule_work(&priv->timeout_work);
> }
>
> -static void timeout_work(struct work_struct *work)
> +static void tpm_timeout_work(struct work_struct *work)
> {
> - struct file_priv *priv = container_of(work, struct file_priv, work);
> + struct file_priv *priv = container_of(work, struct file_priv,
> + timeout_work);
>
> mutex_lock(&priv->buffer_mutex);
> priv->data_pending = 0;
> memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
> mutex_unlock(&priv->buffer_mutex);
> + wake_up_interruptible(&priv->async_wait);
> }
>
> -void tpm_common_open(struct file *file, struct tpm_chip *chip,
> - struct file_priv *priv, struct tpm_space *space)
> +int tpm_common_open(struct file *file, struct tpm_chip *chip,
> + struct file_priv *priv, struct tpm_space *space)
> {
> priv->chip = chip;
> priv->space = space;
>
> mutex_init(&priv->buffer_mutex);
> timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
> - INIT_WORK(&priv->work, timeout_work);
> -
> + INIT_WORK(&priv->timeout_work, tpm_timeout_work);
> + INIT_WORK(&priv->async_work, tpm_async_work);
> + init_waitqueue_head(&priv->async_wait);
> file->private_data = priv;
> + mutex_lock(&tpm_dev_wq_lock);
> + if (!tpm_dev_wq) {
> + tpm_dev_wq = alloc_workqueue("tpm_dev_wq", WQ_MEM_RECLAIM, 0);
> + if (!tpm_dev_wq) {
> + mutex_unlock(&tpm_dev_wq_lock);
> + return -ENOMEM;
> + }
> + }
> +
> + mutex_unlock(&tpm_dev_wq_lock);
> + return 0;
> }
>
> ssize_t tpm_common_read(struct file *file, char __user *buf,
> @@ -63,15 +102,17 @@ ssize_t tpm_common_read(struct file *file, char __user *buf,
> int rc;
>
> del_singleshot_timer_sync(&priv->user_read_timer);
> - flush_work(&priv->work);
> + flush_work(&priv->timeout_work);
> mutex_lock(&priv->buffer_mutex);
>
> if (priv->data_pending) {
> ret_size = min_t(ssize_t, size, priv->data_pending);
> - rc = copy_to_user(buf, priv->data_buffer, ret_size);
> - memset(priv->data_buffer, 0, priv->data_pending);
> - if (rc)
> - ret_size = -EFAULT;
> + if (ret_size > 0) {
> + rc = copy_to_user(buf, priv->data_buffer, ret_size);
> + memset(priv->data_buffer, 0, priv->data_pending);
> + if (rc)
> + ret_size = -EFAULT;
> + }
>
> priv->data_pending = 0;
> }
> @@ -84,10 +125,9 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
> size_t size, loff_t *off)
> {
> struct file_priv *priv = file->private_data;
> - size_t in_size = size;

/Jarkko

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