Re: [PATCH v2] spmi: core: Add generic DebugFS interface for bus inspection

[Abel Vesa]

On 26-10-16 22:00:58, vamshi gajjela wrote:
> Introduce a generic, controller-agnostic DebugFS interface in the SPMI
> core under /sys/kernel/debug/spmi/spmi-<nr>/:
> - name: Displays the controller parent device name and OF node.
> - detect: Probes the bus for active slave IDs (0x0 to 0xF).
> - xfer: Transactional interface supporting register reads, writes,
>   and directed command opcodes with automatic opcode selection.
> 
> Write and command operations restrict access to root (mode 0600) and
> mark the kernel tainted with TAINT_USER. Runtime PM is managed
> automatically across transactions.
> 
> Detailed interface syntax and parameters are documented in
> Documentation/ABI/testing/debugfs-spmi.
> 
> Co-developed-by: Jim Wylder <jwylder@xxxxxxxxxx>
> Signed-off-by: Jim Wylder <jwylder@xxxxxxxxxx>
> Signed-off-by: vamshi gajjela <vamshigajjela@xxxxxxxxxx>
> ---
> Changes in v2:
> - Rename spmi.c to spmi-core.c and link spmi-debugfs.o into the composite
>   spmi.o module so CONFIG_SPMI=m builds cleanly with CONFIG_DEBUG_FS=y.
> - Route DebugFS bus operations through spmi_read_cmd(), spmi_write_cmd(),
>   and spmi_cmd() instead of calling controller callbacks directly,
>   preserving SPMI tracepoints and core validation.
> - Allocate a per-open-file struct spmi_xfer_ctx in open() instead of
>   sharing a controller-wide buffer, avoiding races across concurrent file
>   descriptors, and store struct dentry *debugfs directly on
>   struct spmi_controller.
> - Reset *ppos = 0 on register read commands so repeated transactions on
>   the same open file descriptor work without manual seeking.
> - Restrict SPMI_CMD_ZERO_WRITE at address 0x00 to 7-bit payloads
>   (data[0] <= 0x7f) per the MIPI SPMI specification, falling back to
>   SPMI_CMD_WRITE for 8-bit values.
> - Parse register addresses with kstrtou16() so values above 0xffff are
>   rejected instead of silently truncated.
> - Update Documentation/ABI/testing/debugfs-spmi to document per-fd xfer
>   buffers and 7-bit Zero Write opcode selection.
> 
>  Documentation/ABI/testing/debugfs-spmi |  77 +++++
>  MAINTAINERS                            |   1 +
>  drivers/spmi/Makefile                  |   2 +
>  drivers/spmi/{spmi.c => spmi-core.c}   |  18 +-
>  drivers/spmi/spmi-debugfs.c            | 380 +++++++++++++++++++++++++
>  include/linux/spmi.h                   |  24 ++
>  6 files changed, 496 insertions(+), 6 deletions(-)
>  create mode 100644 Documentation/ABI/testing/debugfs-spmi
>  rename drivers/spmi/{spmi.c => spmi-core.c} (97%)
>  create mode 100644 drivers/spmi/spmi-debugfs.c
> 

[...]

> diff --git a/include/linux/spmi.h b/include/linux/spmi.h
> index 28e8c8bd3944..237b0b9d4377 100644
> --- a/include/linux/spmi.h
> +++ b/include/linux/spmi.h
> @@ -69,6 +69,8 @@ int spmi_device_add(struct spmi_device *sdev);
>  
>  void spmi_device_remove(struct spmi_device *sdev);
>  
> +struct dentry;
> +
>  /**
>   * struct spmi_controller - interface to the SPMI master controller
>   * @dev:	Driver model representation of the device.
> @@ -76,6 +78,7 @@ void spmi_device_remove(struct spmi_device *sdev);
>   * @cmd:	sends a non-data command sequence on the SPMI bus.
>   * @read_cmd:	sends a register read command sequence on the SPMI bus.
>   * @write_cmd:	sends a register write command sequence on the SPMI bus.
> + * @debugfs:	debugfs dentry for this controller.
>   */
>  struct spmi_controller {
>  	struct device		dev;
> @@ -85,6 +88,9 @@ struct spmi_controller {
>  			    u8 sid, u16 addr, u8 *buf, size_t len);
>  	int	(*write_cmd)(struct spmi_controller *ctrl, u8 opcode,
>  			     u8 sid, u16 addr, const u8 *buf, size_t len);
> +#if IS_ENABLED(CONFIG_DEBUG_FS)
> +	struct dentry		*debugfs;
> +#endif
>  };
>  
>  static inline struct spmi_controller *to_spmi_controller(struct device *d)
> @@ -186,4 +192,22 @@ int spmi_command_sleep(struct spmi_device *sdev);
>  int spmi_command_wakeup(struct spmi_device *sdev);
>  int spmi_command_shutdown(struct spmi_device *sdev);
>  
> +int spmi_cmd(struct spmi_controller *ctrl, u8 opcode, u8 sid);
> +int spmi_read_cmd(struct spmi_controller *ctrl, u8 opcode,
> +		  u8 sid, u16 addr, u8 *buf, size_t len);
> +int spmi_write_cmd(struct spmi_controller *ctrl, u8 opcode,
> +		   u8 sid, u16 addr, const u8 *buf, size_t len);

These are not exported, so they can only be used from within spmi.o.
Please move them (together with the debugfs prototypes below) to a
local header in drivers/spmi/ instead of the public include/linux/spmi.h.