Re: [PATCH] usb: typec: intel_pmc_mux: Expose IOM port status to debugfs

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Mar 30, 2023 at 04:18:21PM +0530, Rajat Khandelwal wrote:
> IOM status has a crucial role during debugging to check the
> current state of the type-C port.
> There are ways to fetch the status, but all those require the
> IOM port status offset, which could change with platform.
> 
> Make a debugfs directory for intel_pmc_mux and expose the status
> under it per port basis.
> 
> Signed-off-by: Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
>  drivers/usb/typec/mux/intel_pmc_mux.c | 44 +++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/drivers/usb/typec/mux/intel_pmc_mux.c b/drivers/usb/typec/mux/intel_pmc_mux.c
> index 34e4188a40ff..c99d20888f5d 100644
> --- a/drivers/usb/typec/mux/intel_pmc_mux.c
> +++ b/drivers/usb/typec/mux/intel_pmc_mux.c
> @@ -15,6 +15,7 @@
>  #include <linux/usb/typec_mux.h>
>  #include <linux/usb/typec_dp.h>
>  #include <linux/usb/typec_tbt.h>
> +#include <linux/debugfs.h>
>  
>  #include <asm/intel_scu_ipc.h>
>  
> @@ -145,6 +146,8 @@ struct pmc_usb {
>  	u32 iom_port_status_offset;
>  };
>  
> +static struct dentry *pmc_mux_debugfs_root;

Why not just look up the dentry and delete it when you want it with a
call to debugfs_lookup_and_remove() instead?  That way you don't have to
keep it around (hint, pass it back from your call to
pmc_mux_debugfs_init() or better yet, don't even have a
pmc_mux_debugfs_init() function as it only contains one line and is
only called in one place.

This will save you the storage space of this variable if debugfs is not
enabled in your kernel.  A small amount, yes, but it's nicer, right?

thanks,

greg k-h