Re: [PATCH v2] usb: gadget: f_uac2: Expose all string descriptors through configfs.

From: Pavel Hofman
Date: Tue Apr 23 2024 - 11:39:00 EST


On 23. 04. 24 16:09, Chris Wulff wrote:
> This makes all string descriptors configurable for the UAC2 gadget
> so the user can configure names of terminals/controls/alt modes.
>
> Signed-off-by: Chris Wulff <chris.wulff@xxxxxxxxx>
> ---
> v2: Improved naming of parameters to be mode user friendly. Added documentation.
> v1: https://lore.kernel.org/linux-usb/CO1PR17MB5419B50F94A0014647542931E10D2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
>
> .../ABI/testing/configfs-usb-gadget-uac2 | 13 +++
> Documentation/usb/gadget-testing.rst | 13 +++
> drivers/usb/gadget/function/f_uac2.c | 80 +++++++++++++++----
> drivers/usb/gadget/function/u_uac2.h | 17 +++-
> 4 files changed, 105 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uac2 b/Documentation/ABI/testing/configfs-usb-gadget-uac2
> index a2bf4fd82a5b..250f8eeb8eab 100644
> --- a/Documentation/ABI/testing/configfs-usb-gadget-uac2
> +++ b/Documentation/ABI/testing/configfs-usb-gadget-uac2
> @@ -35,6 +35,19 @@ Description:
> req_number the number of pre-allocated requests
> for both capture and playback
> function_name name of the interface
> + if_ctrl_name topology control name
> + clksrc_in_name input clock name
> + clksrc_out_name output clock name
> + p_it_name playback input terminal name
> + p_ot_name playback output terminal name
> + p_fu_name playback function unit name
> + p_alt0_name playback alt mode 0 name
> + p_alt1_name playback alt mode 1 name

Nacked-by: Pavel Hofman <pavel.hofman@xxxxxxxxxxx>

I am not sure adding a numbered parameter for every additional alt mode
is a way to go for the future. I am not that much concerned about UAC1,
but IMO (at least) in UAC2 the configuration method should be flexible
for more alt setttings. I can see use cases with many more altsettings.

My proposal for adding more alt settings
https://lore.kernel.org/linux-usb/35be4668-58d3-894a-72cf-de1afaacae45@xxxxxxxxxxx/
suggested using lists to existing parameters where each item would
correspond to the alt setting of the same index (+1). That would allow
using more altsettings easily, without having to add parameters to the
source code and adding configfs params. I received no feedback. I do not
push the param list proposal, but I am convinced an acceptable solution
should be discussed thoroughly by the UAC2 gadget stakeholders.

I am afraid that once p_alt1_name/c_alt1_name params are accepted, there
will be no way back because subsequent removal of configfs params could
be viewed as a regression for users.

Thanks a lot for considering,

Pavel.

> + c_it_name capture input terminal name
> + c_ot_name capture output terminal name
> + c_fu_name capture functional unit name
> + c_alt0_name capture alt mode 0 name
> + c_alt1_name capture alt mode 1 name
> c_terminal_type code of the capture terminal type
> p_terminal_type code of the playback terminal type> ===================== =======================================
> diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
> index b086c7ab72f0..1a11d3b3bb88 100644
> --- a/Documentation/usb/gadget-testing.rst
> +++ b/Documentation/usb/gadget-testing.rst
> @@ -765,6 +765,19 @@ The uac2 function provides these attributes in its function directory:
> req_number the number of pre-allocated request for both capture
> and playback
> function_name name of the interface
> + if_ctrl_name topology control name
> + clksrc_in_name input clock name
> + clksrc_out_name output clock name
> + p_it_name playback input terminal name
> + p_ot_name playback output terminal name
> + p_fu_name playback function unit name
> + p_alt0_name playback alt mode 0 name
> + p_alt1_name playback alt mode 1 name
> + c_it_name capture input terminal name
> + c_ot_name capture output terminal name
> + c_fu_name capture functional unit name
> + c_alt0_name capture alt mode 0 name
> + c_alt1_name capture alt mode 1 name
> c_terminal_type code of the capture terminal type
> p_terminal_type code of the playback terminal type
> ================ ====================================================
> diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
> index 383f6854cfec..5ca7ecdb6e60 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -104,25 +104,10 @@ enum {
> STR_AS_OUT_ALT1,
> STR_AS_IN_ALT0,
> STR_AS_IN_ALT1,
> + NUM_STR_DESCRIPTORS,
> };
>
> -static struct usb_string strings_fn[] = {
> - /* [STR_ASSOC].s = DYNAMIC, */
> - [STR_IF_CTRL].s = "Topology Control",
> - [STR_CLKSRC_IN].s = "Input Clock",
> - [STR_CLKSRC_OUT].s = "Output Clock",
> - [STR_USB_IT].s = "USBH Out",
> - [STR_IO_IT].s = "USBD Out",
> - [STR_USB_OT].s = "USBH In",
> - [STR_IO_OT].s = "USBD In",
> - [STR_FU_IN].s = "Capture Volume",
> - [STR_FU_OUT].s = "Playback Volume",
> - [STR_AS_OUT_ALT0].s = "Playback Inactive",
> - [STR_AS_OUT_ALT1].s = "Playback Active",
> - [STR_AS_IN_ALT0].s = "Capture Inactive",
> - [STR_AS_IN_ALT1].s = "Capture Active",
> - { },
> -};
> +static struct usb_string strings_fn[NUM_STR_DESCRIPTORS + 1] = {};
>
> static const char *const speed_names[] = {
> [USB_SPEED_UNKNOWN] = "UNKNOWN",
> @@ -1049,6 +1034,21 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
> return ret;
>
> strings_fn[STR_ASSOC].s = uac2_opts->function_name;
> + strings_fn[STR_IF_CTRL].s = uac2_opts->if_ctrl_name;
> + strings_fn[STR_CLKSRC_IN].s = uac2_opts->clksrc_in_name;
> + strings_fn[STR_CLKSRC_OUT].s = uac2_opts->clksrc_out_name;
> +
> + strings_fn[STR_USB_IT].s = uac2_opts->p_it_name;
> + strings_fn[STR_IO_OT].s = uac2_opts->p_ot_name;
> + strings_fn[STR_FU_OUT].s = uac2_opts->p_fu_name;
> + strings_fn[STR_AS_OUT_ALT0].s = uac2_opts->p_alt0_name;
> + strings_fn[STR_AS_OUT_ALT1].s = uac2_opts->p_alt1_name;
> +
> + strings_fn[STR_IO_IT].s = uac2_opts->c_it_name;
> + strings_fn[STR_USB_OT].s = uac2_opts->c_ot_name;
> + strings_fn[STR_FU_IN].s = uac2_opts->c_fu_name;
> + strings_fn[STR_AS_IN_ALT0].s = uac2_opts->c_alt0_name;
> + strings_fn[STR_AS_IN_ALT1].s = uac2_opts->c_alt1_name;
>
> us = usb_gstrings_attach(cdev, fn_strings, ARRAY_SIZE(strings_fn));
> if (IS_ERR(us))
> @@ -2097,10 +2097,26 @@ UAC2_ATTRIBUTE(s16, c_volume_max);
> UAC2_ATTRIBUTE(s16, c_volume_res);
> UAC2_ATTRIBUTE(u32, fb_max);
> UAC2_ATTRIBUTE_STRING(function_name);
> +UAC2_ATTRIBUTE_STRING(if_ctrl_name);
> +UAC2_ATTRIBUTE_STRING(clksrc_in_name);
> +UAC2_ATTRIBUTE_STRING(clksrc_out_name);
> +
> +UAC2_ATTRIBUTE_STRING(p_it_name);
> +UAC2_ATTRIBUTE_STRING(p_ot_name);
> +UAC2_ATTRIBUTE_STRING(p_fu_name);
> +UAC2_ATTRIBUTE_STRING(p_alt0_name);
> +UAC2_ATTRIBUTE_STRING(p_alt1_name);
> +
> +UAC2_ATTRIBUTE_STRING(c_it_name);
> +UAC2_ATTRIBUTE_STRING(c_ot_name);
> +UAC2_ATTRIBUTE_STRING(c_fu_name);
> +UAC2_ATTRIBUTE_STRING(c_alt0_name);
> +UAC2_ATTRIBUTE_STRING(c_alt1_name);
>
> UAC2_ATTRIBUTE(s16, p_terminal_type);
> UAC2_ATTRIBUTE(s16, c_terminal_type);
>
> +
> static struct configfs_attribute *f_uac2_attrs[] = {
> &f_uac2_opts_attr_p_chmask,
> &f_uac2_opts_attr_p_srate,
> @@ -2127,6 +2143,21 @@ static struct configfs_attribute *f_uac2_attrs[] = {
> &f_uac2_opts_attr_c_volume_res,
>
> &f_uac2_opts_attr_function_name,
> + &f_uac2_opts_attr_if_ctrl_name,
> + &f_uac2_opts_attr_clksrc_in_name,
> + &f_uac2_opts_attr_clksrc_out_name,
> +
> + &f_uac2_opts_attr_p_it_name,
> + &f_uac2_opts_attr_p_ot_name,
> + &f_uac2_opts_attr_p_fu_name,
> + &f_uac2_opts_attr_p_alt0_name,
> + &f_uac2_opts_attr_p_alt1_name,
> +
> + &f_uac2_opts_attr_c_it_name,
> + &f_uac2_opts_attr_c_ot_name,
> + &f_uac2_opts_attr_c_fu_name,
> + &f_uac2_opts_attr_c_alt0_name,
> + &f_uac2_opts_attr_c_alt1_name,
>
> &f_uac2_opts_attr_p_terminal_type,
> &f_uac2_opts_attr_c_terminal_type,
> @@ -2188,6 +2219,21 @@ static struct usb_function_instance *afunc_alloc_inst(void)
> opts->fb_max = FBACK_FAST_MAX;
>
> scnprintf(opts->function_name, sizeof(opts->function_name), "Source/Sink");
> + scnprintf(opts->if_ctrl_name, sizeof(opts->if_ctrl_name), "Topology Control");
> + scnprintf(opts->clksrc_in_name, sizeof(opts->clksrc_in_name), "Input Clock");
> + scnprintf(opts->clksrc_out_name, sizeof(opts->clksrc_out_name), "Output Clock");
> +
> + scnprintf(opts->p_it_name, sizeof(opts->p_it_name), "USBH Out");
> + scnprintf(opts->p_ot_name, sizeof(opts->p_ot_name), "USBD In");
> + scnprintf(opts->p_fu_name, sizeof(opts->p_fu_name), "Playback Volume");
> + scnprintf(opts->p_alt0_name, sizeof(opts->p_alt0_name), "Playback Inactive");
> + scnprintf(opts->p_alt1_name, sizeof(opts->p_alt1_name), "Playback Active");
> +
> + scnprintf(opts->c_it_name, sizeof(opts->c_it_name), "USBD Out");
> + scnprintf(opts->c_ot_name, sizeof(opts->c_ot_name), "USBH In");
> + scnprintf(opts->c_fu_name, sizeof(opts->c_fu_name), "Capture Volume");
> + scnprintf(opts->c_alt0_name, sizeof(opts->c_alt0_name), "Capture Inactive");
> + scnprintf(opts->c_alt1_name, sizeof(opts->c_alt1_name), "Capture Active");
>
> opts->p_terminal_type = UAC2_DEF_P_TERM_TYPE;
> opts->c_terminal_type = UAC2_DEF_C_TERM_TYPE;
> diff --git a/drivers/usb/gadget/function/u_uac2.h b/drivers/usb/gadget/function/u_uac2.h
> index 5e81bdd6c5fb..e697d35a1759 100644
> --- a/drivers/usb/gadget/function/u_uac2.h
> +++ b/drivers/usb/gadget/function/u_uac2.h
> @@ -68,7 +68,22 @@ struct f_uac2_opts {
> int fb_max;
> bool bound;
>
> - char function_name[32];
> + char function_name[USB_MAX_STRING_LEN];
> + char if_ctrl_name[USB_MAX_STRING_LEN];
> + char clksrc_in_name[USB_MAX_STRING_LEN];
> + char clksrc_out_name[USB_MAX_STRING_LEN];
> +
> + char p_it_name[USB_MAX_STRING_LEN];
> + char p_ot_name[USB_MAX_STRING_LEN];
> + char p_fu_name[USB_MAX_STRING_LEN];
> + char p_alt0_name[USB_MAX_STRING_LEN];
> + char p_alt1_name[USB_MAX_STRING_LEN];
> +
> + char c_it_name[USB_MAX_STRING_LEN];
> + char c_ot_name[USB_MAX_STRING_LEN];
> + char c_fu_name[USB_MAX_STRING_LEN];
> + char c_alt0_name[USB_MAX_STRING_LEN];
> + char c_alt1_name[USB_MAX_STRING_LEN];
>
> s16 p_terminal_type;
> s16 c_terminal_type;