[v6,0/4] user space client interface driver

V6:
- Moved uci.c to mhi directory.
- Updated Kconfig to add module information.
- Updated Makefile to rename uci object file name as mhi_uci
- Removed kref for open count

V5:
- Removed mhi_uci_drv structure.
- Used idr instead of creating global list of uci devices.
- Used kref instead of local ref counting for uci device and
  open count.
- Removed unlikely macro.

V4:
- Fix locking to protect proper struct members.
- Updated documentation describing uci client driver use cases.
- Fixed uci ref counting in mhi_uci_open for error case.
- Addressed style related review comments.

V3: Added documentation for MHI UCI driver.

V2: Added mutex lock to prevent multiple readers to access same
mhi buffer which can result into use after free.

Hemant Kumar (4):
  bus: mhi: core: Add helper API to return number of free TREs
  bus: mhi: core: Move MHI_MAX_MTU to external header file
  docs: Add documentation for userspace client interface
  bus: mhi: Add userspace client interface driver

 Documentation/mhi/index.rst     |   1 +
 Documentation/mhi/uci.rst       |  39 +++
 drivers/bus/mhi/Kconfig         |  13 +
 drivers/bus/mhi/Makefile        |   4 +
 drivers/bus/mhi/core/internal.h |   1 -
 drivers/bus/mhi/core/main.c     |  12 +
 drivers/bus/mhi/uci.c           | 657 ++++++++++++++++++++++++++++++++++++++++
 include/linux/mhi.h             |  12 +
 8 files changed, 738 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/mhi/uci.rst
 create mode 100644 drivers/bus/mhi/uci.c

"user space client interface driver" is a very generic and there is
absolutel no explanation in this cover letter.  What is this supposed
to be?

On Wed, Sep 16, 2020 at 12:56:04PM -0700, Hemant Kumar wrote:
> Introduce mhi_get_no_free_descriptors() API to return number
> of TREs available to queue buffer. MHI clients can use this
> API to know before hand if ring is full without calling queue
> API.
> 
> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
> ---
>  drivers/bus/mhi/core/main.c | 12 ++++++++++++
>  include/linux/mhi.h         |  9 +++++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 2cff5dd..0599e7d 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -258,6 +258,18 @@ int mhi_destroy_device(struct device *dev, void *data)
>  	return 0;
>  }
>  
> +int mhi_get_no_free_descriptors(struct mhi_device *mhi_dev,
> +				enum dma_data_direction dir)
> +{
> +	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
> +	struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ?
> +		mhi_dev->ul_chan : mhi_dev->dl_chan;
> +	struct mhi_ring *tre_ring = &mhi_chan->tre_ring;
> +
> +	return get_nr_avail_ring_elements(mhi_cntrl, tre_ring);

Hmm, so this is essentially a wrapper for get_nr_avail_ring_elements().
Why can't you call this API directly?

> +}
> +EXPORT_SYMBOL_GPL(mhi_get_no_free_descriptors);
> +
>  void mhi_notify(struct mhi_device *mhi_dev, enum mhi_callback cb_reason)
>  {
>  	struct mhi_driver *mhi_drv;
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index a35d876..6565528 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -600,6 +600,15 @@ void mhi_set_mhi_state(struct mhi_controller *mhi_cntrl,
>  void mhi_notify(struct mhi_device *mhi_dev, enum mhi_callback cb_reason);
>  
>  /**
> + * mhi_get_no_free_descriptors - Get transfer ring length

mhi_get_nr_free_descriptors?

> + * Get # of TD available to queue buffers
> + * @mhi_dev: Device associated with the channels
> + * @dir: Direction of the channel
> + */
> +int mhi_get_no_free_descriptors(struct mhi_device *mhi_dev,
> +				enum dma_data_direction dir);

Align enum with start of "("

Thanks,
Mani

> +
> +/**
>   * mhi_prepare_for_power_up - Do pre-initialization before power up.
>   *                            This is optional, call this before power up if
>   *                            the controller does not want bus framework to
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>

On Wed, Sep 16, 2020 at 12:56:05PM -0700, Hemant Kumar wrote:
> Currently this macro is defined in internal MHI header as
> a TRE length mask. Moving it to external header allows MHI
> client drivers to set this upper bound for the transmit
> buffer size.
> 
> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/internal.h | 1 -
>  include/linux/mhi.h             | 3 +++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/core/internal.h b/drivers/bus/mhi/core/internal.h
> index 7989269..4abf0cf 100644
> --- a/drivers/bus/mhi/core/internal.h
> +++ b/drivers/bus/mhi/core/internal.h
> @@ -453,7 +453,6 @@ enum mhi_pm_state {
>  #define CMD_EL_PER_RING			128
>  #define PRIMARY_CMD_RING		0
>  #define MHI_DEV_WAKE_DB			127
> -#define MHI_MAX_MTU			0xffff
>  #define MHI_RANDOM_U32_NONZERO(bmsk)	(prandom_u32_max(bmsk) + 1)
>  
>  enum mhi_er_type {
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index 6565528..610f3b0 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -16,6 +16,9 @@
>  #include <linux/wait.h>
>  #include <linux/workqueue.h>
>  
> +/* MHI client drivers to set this upper bound for tx buffer */
> +#define MHI_MAX_MTU 0xffff
> +
>  #define MHI_MAX_OEM_PK_HASH_SEGMENTS 16
>  
>  struct mhi_chan;
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>