Re: [PATCH] HID: logitech-hidpp: Add support for HID++ Multi-Platform feature (0x4531)

[dev exalt]

Dear maintainers,


We would like to kindly follow up on this patch sent on Dec 15, 2025,
as we haven't received feedback yet.

Patch link:
https://lore.kernel.org/linux-input/20251215125319.33261-1-exalt.dev.team@xxxxxxxxx/T/#u

We understand maintainers are busy, so just sending a gentle reminder
in case this slipped.

Thank you for your time and review.


Best regards,

Baraa Atta (Dev Exalt) <exalt.dev.team@xxxxxxxxx>


On Sun, Mar 8, 2026 at 10:01 AM dev exalt <exalt.dev.team@xxxxxxxxx> wrote:
>
> Dear maintainers,
>
>
> We would like to kindly follow up on this patch sent on Dec 15, 2025, as we haven't received feedback yet.
>
> Patch link:
> https://lore.kernel.org/linux-input/20251215125319.33261-1-exalt.dev.team@xxxxxxxxx/T/#u
>
> We understand maintainers are busy, so just sending a gentle reminder in case this slipped.
>
> Thank you for your time and review.
>
>
> Best regards,
>
> Baraa Atta (Dev Exalt) <exalt.dev.team@xxxxxxxxx>
>
>
> On Mon, Dec 15, 2025 at 2:53 PM DevExalt <exalt.dev.team@xxxxxxxxx> wrote:
>>
>> From: "Baraa Atta (Dev Exalt)" <exalt.dev.team@xxxxxxxxx>
>>
>> Add support in the Logitech HID++ driver for the HID++ Multi-Platform
>> feature (0x4531), which enables HID++ devices to adjust their behavior
>> based on the host operating system (Linux, ChromeOS, Android).
>>
>> This patch:
>>  * Adds device IDs for MX Keys S (046d:b378) and Casa Keys (046d:b371).
>>  * Introduces the module parameter "hidpp_platform" to allow selecting a
>>    target platform.
>>  * Detects whether a device implements feature 0x4531.
>>  * Validates that the requested platform is supported by the device.
>>  * Applies the platform index when valid, otherwise leaves the device
>>    unchanged.
>>  * Keeps default behavior when "hidpp_platform" is unset or invalid.
>>
>> Supported values for hidpp_platform:
>>    Android, Linux, Chrome
>>
>> TEST=Pair MX Keys S and Casa Keys over Bluetooth and verify:
>>      * Feature 0x4531 is detected.
>>      * Valid platform values are accepted and applied.
>>      * Invalid platform values result in no update.
>>      * Devices without 0x4531 retain default behavior.
>>      * Platform-specific key behavior is observed once applied.
>>
>> Signed-off-by: Baraa Atta (Dev Exalt) <exalt.dev.team@xxxxxxxxx>
>> ---
>>  drivers/hid/hid-ids.h            |   2 +
>>  drivers/hid/hid-logitech-hidpp.c | 280 +++++++++++++++++++++++++++++++
>>  drivers/hid/hid-quirks.c         |   2 +
>>  3 files changed, 284 insertions(+)
>>
>> diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
>> index d31711f1aaec..12de1194d7fa 100644
>> --- a/drivers/hid/hid-ids.h
>> +++ b/drivers/hid/hid-ids.h
>> @@ -866,6 +866,8 @@
>>  #define USB_DEVICE_ID_LOGITECH_T651    0xb00c
>>  #define USB_DEVICE_ID_LOGITECH_DINOVO_EDGE_KBD 0xb309
>>  #define USB_DEVICE_ID_LOGITECH_CASA_TOUCHPAD   0xbb00
>> +#define USB_DEVICE_ID_LOGITECH_CASA_KEYS_KEYBOARD      0xb371
>> +#define USB_DEVICE_ID_LOGITECH_MX_KEYS_S_KEYBOARD      0xb378
>>  #define USB_DEVICE_ID_LOGITECH_C007    0xc007
>>  #define USB_DEVICE_ID_LOGITECH_C077    0xc077
>>  #define USB_DEVICE_ID_LOGITECH_RECEIVER        0xc101
>> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
>> index d5011a5d0890..e94daed31981 100644
>> --- a/drivers/hid/hid-logitech-hidpp.c
>> +++ b/drivers/hid/hid-logitech-hidpp.c
>> @@ -4373,6 +4373,280 @@ static bool hidpp_application_equals(struct hid_device *hdev,
>>         return report && report->application == application;
>>  }
>>
>> +/* -------------------------------------------------------------------------- */
>> +/* 0x4531: Multi-Platform Support                                             */
>> +/* -------------------------------------------------------------------------- */
>> +
>> +/*
>> + * Some Logitech devices expose the HID++ feature 0x4531 (Multi-Platform) allowing
>> + * the host to specify which operating system platform to use on the device. Changing device's
>> + * platform may alter the behavior of the device to match the specified platform.
>> + */
>> +
>> +static char *hidpp_platform;
>> +module_param(hidpp_platform, charp, 0644);
>> +MODULE_PARM_DESC(hidpp_platform, "Select host platform type for Logitech HID++ Multi-Platform feature "
>> +                "0x4531, valid values: (linux|chrome|android).  If unset, no "
>> +                "change is applied.");
>> +
>> +#define HIDPP_MULTIPLATFORM_FEAT_ID                    0x4531
>> +#define HIDPP_MULTIPLATFORM_GET_FEATURE_INFO           0x0F
>> +#define HIDPP_MULTIPLATFORM_GET_PLATFORM_DESCRIPTOR    0x1F
>> +#define HIDPP_MULTIPLATFORM_SET_CURRENT_PLATFORM       0x3F
>> +
>> +#define HIDPP_MULTIPLATFORM_PLATFORM_MASK_LINUX                BIT(10)
>> +#define HIDPP_MULTIPLATFORM_PLATFORM_MASK_CHROME       BIT(11)
>> +#define HIDPP_MULTIPLATFORM_PLATFORM_MASK_ANDROID      BIT(12)
>> +
>> +struct hidpp_platform_desc {
>> +       u8 plat_idx;
>> +       u8 desc_idx;
>> +       u16 plat_mask;
>> +};
>> +
>> +/**
>> + * hidpp_multiplatform_mask_from_str() - Convert platform name to an HID++ platform mask
>> + * @pname: Platform name string
>> + *
>> + * Converts a platform name string to its corresponding HID++ platform mask based on
>> + * the Multi-Platform feature specification.
>> + *
>> + * Return: Platform mask corresponding to @pname on success,
>> + * or 0 if @pname is NULL or unsupported.
>> + */
>> +static u16 hidpp_multiplatform_mask_from_str(const char *pname)
>> +{
>> +       if (!pname)
>> +               return 0;
>> +
>> +       if (!strcasecmp(pname, "linux"))
>> +               return HIDPP_MULTIPLATFORM_PLATFORM_MASK_LINUX;
>> +       if (!strcasecmp(pname, "chrome"))
>> +               return HIDPP_MULTIPLATFORM_PLATFORM_MASK_CHROME;
>> +       if (!strcasecmp(pname, "android"))
>> +               return HIDPP_MULTIPLATFORM_PLATFORM_MASK_ANDROID;
>> +
>> +       return 0;
>> +}
>> +
>> +/**
>> + * hidpp_multiplatform_get_num_pdesc() - Retrieve number of platform descriptors
>> + * @hidpp: Pointer to the hidpp_device instance
>> + * @feat_index: Feature index of the Multi-Platform feature
>> + * @num_desc: Pointer to store the number of platform descriptors
>> + *
>> + * Retrieves the number of platform descriptors supported by the device through
>> + * the Multi-Platform feature and stores it in @num_desc.
>> + *
>> + * Return: 0 on success, or non-zero on failure.
>> + */
>> +static int hidpp_multiplatform_get_num_pdesc(struct hidpp_device *hidpp,
>> +                                            u8 feat_index, u8 *num_desc)
>> +{
>> +       int ret;
>> +       struct hidpp_report response;
>> +       struct hid_device *hdev = hidpp->hid_dev;
>> +
>> +       ret = hidpp_send_fap_command_sync(hidpp, feat_index,
>> +                                         HIDPP_MULTIPLATFORM_GET_FEATURE_INFO,
>> +                                         NULL, 0, &response);
>> +       if (ret) {
>> +               hid_warn(hdev, "Multiplatform: GET_FEATURE_INFO failed (err=%d)", ret);
>> +               return ret;
>> +       }
>> +
>> +       *num_desc = response.fap.params[3];
>> +       hid_dbg(hdev, "Multiplatform: Device supports %d platform descriptors", *num_desc);
>> +
>> +       return 0;
>> +}
>> +
>> +/**
>> + * hidpp_multiplatform_get_platform_desc() - Retrieve a platform descriptor entry
>> + * @hidpp: Pointer to the hidpp_device instance
>> + * @feat_index: Feature index of the Multi-Platform feature
>> + * @platform_idx: Index of the platform descriptor to retrieve
>> + * @pdesc: Pointer to store the retrieved platform descriptor
>> + *
>> + * Retrieves a single platform descriptor identified by @platform_idx from the
>> + * device and stores the parsed descriptor fields in @pdesc.
>> + *
>> + * Return: 0 on success, or non-zero on failure.
>> + */
>> +static int hidpp_multiplatform_get_platform_desc(struct hidpp_device *hidpp, u8 feat_index,
>> +                                                u8 platform_idx, struct hidpp_platform_desc *pdesc)
>> +{
>> +       int ret;
>> +       struct hidpp_report response;
>> +       u8 params[1] = { platform_idx };
>> +       struct hid_device *hdev = hidpp->hid_dev;
>> +
>> +       ret = hidpp_send_fap_command_sync(hidpp, feat_index,
>> +                                         HIDPP_MULTIPLATFORM_GET_PLATFORM_DESCRIPTOR,
>> +                                         params, sizeof(params), &response);
>> +
>> +       if (ret) {
>> +               hid_warn(hdev,
>> +                        "Multiplatform: GET_PLATFORM_DESCRIPTOR failed for index %d (err=%d)",
>> +                        platform_idx, ret);
>> +               return ret;
>> +       }
>> +
>> +       pdesc->plat_idx = response.fap.params[0];
>> +       pdesc->desc_idx = response.fap.params[1];
>> +       pdesc->plat_mask = get_unaligned_be16(&response.fap.params[2]);
>> +
>> +       hid_dbg(hdev,
>> +               "Multiplatform: descriptor %d: plat_idx=%d, desc_idx=%d, plat_mask=0x%04x",
>> +               platform_idx, pdesc->plat_idx, pdesc->desc_idx, pdesc->plat_mask);
>> +
>> +       return 0;
>> +}
>> +
>> +/**
>> + * hidpp_multiplatform_get_platform_index() - Find platform index for a mask
>> + * @hidpp: Pointer to the hidpp_device instance
>> + * @feat_index: Feature index of the Multi-Platform feature
>> + * @plat_mask: Platform mask to search for
>> + * @plat_index: Pointer to store the matched platform index
>> + *
>> + * Iterates through all platform descriptors exposed by the device via the
>> + * Multi-Platform feature, retrieving each descriptor and comparing its
>> + * platform mask to @plat_mask. A descriptor matches if its mask overlaps with
>> + * the requested @plat_mask (i.e. (pdesc.plat_mask & plat_mask) is non-zero).
>> + *
>> + * When a matching descriptor is found, its platform index (plat_idx) is
>> + * written to @plat_index and the function returns success.
>> + *
>> + * If no descriptor matches, -ENOENT is returned.
>> + *
>> + * Return: 0 on success; -ENOENT if no matching descriptor exists;
>> + *         or non-zero on failure.
>> + */
>> +static int hidpp_multiplatform_get_platform_index(struct hidpp_device *hidpp,
>> +                                                 u8 feat_index, u16 plat_mask,
>> +                                                 u8 *plat_index)
>> +{
>> +       int i;
>> +       int ret;
>> +       u8 num_desc;
>> +       struct hidpp_platform_desc pdesc;
>> +       struct hid_device *hdev = hidpp->hid_dev;
>> +
>> +       ret = hidpp_multiplatform_get_num_pdesc(hidpp, feat_index, &num_desc);
>> +       if (ret)
>> +               return ret;
>> +
>> +       for (i = 0; i < num_desc; i++) {
>> +               ret = hidpp_multiplatform_get_platform_desc(hidpp, feat_index, i, &pdesc);
>> +               if (ret)
>> +                       return ret;
>> +
>> +               if (pdesc.plat_mask & plat_mask) {
>> +                       *plat_index = pdesc.plat_idx;
>> +                       hid_dbg(hdev,
>> +                               "Multiplatform: Selected platform index %d for platform '%s'",
>> +                               *plat_index, hidpp_platform);
>> +                       return 0;
>> +               }
>> +       }
>> +
>> +       hid_dbg(hdev,
>> +               "Multiplatform: No matching platform descriptor found for platform '%s'",
>> +               hidpp_platform);
>> +       return -ENOENT;
>> +}
>> +
>> +/**
>> + * hidpp_multiplatform_update_device_platform() - Update the device platform
>> + * @hidpp: Pointer to the hidpp_device instance
>> + * @feat_index: Feature index of the Multi-Platform feature
>> + * @plat_index: Platform index to set on the device
>> + *
>> + * Sends the HID++ Multi-Platform 'SET_CURRENT_PLATFORM' command to the device to
>> + * update its platform index to @plat_index.
>> + *
>> + * Return: 0 on success, or non-zero on failure.
>> + */
>> +static int hidpp_multiplatform_update_device_platform(struct hidpp_device *hidpp,
>> +                                                     u8 feat_index, u8 plat_index)
>> +{
>> +       int ret;
>> +       struct hidpp_report response;
>> +       /* Byte 0 (hostIndex): 0xFF selects the current host. */
>> +       u8 params[2] = { 0xFF, plat_index };
>> +
>> +       ret = hidpp_send_fap_command_sync(hidpp, feat_index,
>> +                                         HIDPP_MULTIPLATFORM_SET_CURRENT_PLATFORM,
>> +                                         params, sizeof(params), &response);
>> +
>> +       if (ret)
>> +               hid_warn(hidpp->hid_dev,
>> +                        "Multiplatform: SET_CURRENT_PLATFORM failed for index %d (err=%d)",
>> +                        plat_index, ret);
>> +
>> +       return ret;
>> +}
>> +
>> +/**
>> + * hidpp_multiplatform_init() - Apply the HID++ Multi-Platform (0x4531) feature
>> + * @hidpp: Pointer to the hidpp_device instance
>> + *
>> + * Initializes the Multi-Platform feature by selecting the device platform
>> + * corresponding to the module parameter @hidpp_platform, if provided.
>> + *
>> + * The function performs the following steps:
>> + *   1. Convert the @hidpp_platform string into a platform mask.
>> + *   2. Check whether the device supports the Multi-Platform feature (0x4531).
>> + *   3. Look up the device's platform index whose mask matches the host
>> + *      platform mask.
>> + *   4. Apply that platform index to the device via 'SET_CURRENT_PLATFORM'.
>> + *
>> + * If the module parameter is unset or invalid, or the device does not support
>> + * the feature, or no matching platform descriptor is found, the function exits
>> + * silently without modifying the device state.
>> + *
>> + * On success, the device's platform configuration is updated.
>> + */
>> +static void hidpp_multiplatform_init(struct hidpp_device *hidpp)
>> +{
>> +       int ret;
>> +       u8 feat_index;
>> +       u8 plat_index;
>> +       u16 host_plat_mask;
>> +       struct hid_device *hdev = hidpp->hid_dev;
>> +
>> +       if (!hidpp_platform)
>> +               return;
>> +
>> +       host_plat_mask = hidpp_multiplatform_mask_from_str(hidpp_platform);
>> +       if (!host_plat_mask) {
>> +               hid_warn(hdev,
>> +                        "Multiplatform: Invalid or unsupported platform name '%s'",
>> +                        hidpp_platform);
>> +               return;
>> +       }
>> +
>> +       ret = hidpp_root_get_feature(hidpp, HIDPP_MULTIPLATFORM_FEAT_ID, &feat_index);
>> +       if (ret) {
>> +               hid_warn(hdev,
>> +                        "Multiplatform: Failed to get the HID++ multiplatform feature 0x4531");
>> +               return;
>> +       }
>> +
>> +       ret = hidpp_multiplatform_get_platform_index(hidpp, feat_index, host_plat_mask,
>> +                                                    &plat_index);
>> +       if (ret)
>> +               return;
>> +
>> +       ret = hidpp_multiplatform_update_device_platform(hidpp, feat_index, plat_index);
>> +       if (ret)
>> +               return;
>> +
>> +       hid_info(hdev,
>> +                "Multiplatform: Device platform successfully set to '%s'", hidpp_platform);
>> +}
>> +
>>  static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>  {
>>         struct hidpp_device *hidpp;
>> @@ -4467,6 +4741,8 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>         if (hidpp->quirks & HIDPP_QUIRK_DELAYED_INIT)
>>                 connect_mask &= ~HID_CONNECT_HIDINPUT;
>>
>> +       hidpp_multiplatform_init(hidpp);
>> +
>>         /* Now export the actual inputs and hidraw nodes to the world */
>>         hid_device_io_stop(hdev);
>>         ret = hid_connect(hdev, connect_mask);
>> @@ -4664,6 +4940,10 @@ static const struct hid_device_id hidpp_devices[] = {
>>           HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, 0xb034) },
>>         { /* MX Anywhere 3SB mouse over Bluetooth */
>>           HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, 0xb038) },
>> +       { /* Casa Keys keyboard over Bluetooth */
>> +         HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_CASA_KEYS_KEYBOARD) },
>> +       { /* MX Keys S keyboard over Bluetooth */
>> +         HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MX_KEYS_S_KEYBOARD) },
>>         {}
>>  };
>>
>> diff --git a/drivers/hid/hid-quirks.c b/drivers/hid/hid-quirks.c
>> index c89a015686c0..99ca04b61bda 100644
>> --- a/drivers/hid/hid-quirks.c
>> +++ b/drivers/hid/hid-quirks.c
>> @@ -520,6 +520,8 @@ static const struct hid_device_id hid_have_special_driver[] = {
>>  #endif
>>  #if IS_ENABLED(CONFIG_HID_LOGITECH_HIDPP)
>>         { HID_USB_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_G920_WHEEL) },
>> +       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_CASA_KEYS_KEYBOARD) },
>> +       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, USB_DEVICE_ID_LOGITECH_MX_KEYS_S_KEYBOARD) },
>>  #endif
>>  #if IS_ENABLED(CONFIG_HID_MAGICMOUSE)
>>         { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_MAGICMOUSE) },
>> --
>> 2.34.1
>>