Re: [PATCH] HID: add cmedia-fixup driver

This driver provides HID fixups for CMedia audio chips.
For now this enables the recognition of the microphone mute button for the
HS-100B.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/hid/Kconfig            |  6 +++
 drivers/hid/Makefile           |  1 +
 drivers/hid/hid-cmedia-fixup.c | 82 ++++++++++++++++++++++++++++++++++
 drivers/hid/hid-ids.h          |  1 +
 drivers/hid/hid-quirks.c       |  3 ++
 5 files changed, 93 insertions(+)
 create mode 100644 drivers/hid/hid-cmedia-fixup.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 160554903ef9..5e139c93f75a 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig

@@ -264,6 +264,12 @@ config HID_CMEDIA
        help
        Support for CMedia CM6533 HID audio jack controls.

+config HID_CMEDIA_FIXUP
+       tristate "CMedia hid fixup"
+       depends on HID
+       help
+       Fixups for CMedia based audio chips.
+
 config HID_CP2112
        tristate "Silicon Labs CP2112 HID USB-to-SMBus Bridge support"
        depends on USB_HID && HIDRAW && I2C && GPIOLIB

diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index 1ea1a7c0b20f..66d6b06ce4d2 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile

@@ -36,6 +36,7 @@ obj-$(CONFIG_HID_BIGBEN_FF)   += hid-bigbenff.o
 obj-$(CONFIG_HID_CHERRY)       += hid-cherry.o
 obj-$(CONFIG_HID_CHICONY)      += hid-chicony.o
 obj-$(CONFIG_HID_CMEDIA)       += hid-cmedia.o
+obj-$(CONFIG_HID_CMEDIA_FIXUP) += hid-cmedia-fixup.o
 obj-$(CONFIG_HID_CORSAIR)      += hid-corsair.o
 obj-$(CONFIG_HID_COUGAR)       += hid-cougar.o
 obj-$(CONFIG_HID_CP2112)       += hid-cp2112.o

diff --git a/drivers/hid/hid-cmedia-fixup.c b/drivers/hid/hid-cmedia-fixup.c
new file mode 100644
index 000000000000..c9a984ea6f0a
--- /dev/null
+++ b/drivers/hid/hid-cmedia-fixup.c

@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HID driver containing fixups for CMedia audio chips.
+ *
+ * Copyright (C) 2021 Thomas Weißschuh <thomas@weissschuh.net>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+#include "hid-ids.h"
+
+#define HS100B_RDESC_ORIG_SIZE 60
+
+/* Fixed report descriptor of HS-100B audio chip
+ * Bit 4 is an abolute Microphone mute usage instead of being unassigned.
+ */
+static __u8 hs100b_rdesc_fixed[] = {
+       0x05, 0x0C,         /*  Usage Page (Consumer),          */
+       0x09, 0x01,         /*  Usage (Consumer Control),       */
+       0xA1, 0x01,         /*  Collection (Application),       */
+       0x15, 0x00,         /*      Logical Minimum (0),        */
+       0x25, 0x01,         /*      Logical Maximum (1),        */
+       0x09, 0xE9,         /*      Usage (Volume Inc),         */
+       0x09, 0xEA,         /*      Usage (Volume Dec),         */
+       0x75, 0x01,         /*      Report Size (1),            */
+       0x95, 0x02,         /*      Report Count (2),           */
+       0x81, 0x02,         /*      Input (Variable),           */
+       0x09, 0xE2,         /*      Usage (Mute),               */
+       0x95, 0x01,         /*      Report Count (1),           */
+       0x81, 0x06,         /*      Input (Variable, Relative), */
+       0x05, 0x0B,         /*      Usage Page (Telephony),     */
+       0x09, 0x2F,         /*      Usage (2Fh),                */
+       0x81, 0x02,         /*      Input (Variable),           */
+       0x09, 0x20,         /*      Usage (20h),                */
+       0x81, 0x06,         /*      Input (Variable, Relative), */
+       0x05, 0x0C,         /*      Usage Page (Consumer),      */
+       0x09, 0x00,         /*      Usage (00h),                */
+       0x95, 0x03,         /*      Report Count (3),           */
+       0x81, 0x02,         /*      Input (Variable),           */
+       0x26, 0xFF, 0x00,   /*      Logical Maximum (255),      */
+       0x09, 0x00,         /*      Usage (00h),                */
+       0x75, 0x08,         /*      Report Size (8),            */
+       0x95, 0x03,         /*      Report Count (3),           */
+       0x81, 0x02,         /*      Input (Variable),           */
+       0x09, 0x00,         /*      Usage (00h),                */
+       0x95, 0x04,         /*      Report Count (4),           */
+       0x91, 0x02,         /*      Output (Variable),          */
+       0xC0                /*  End Collection                  */
+};
+
+static __u8 *cmhid_fixup_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+                                     unsigned int *rsize)
+{
+       switch (hdev->product) {
+       case USB_DEVICE_ID_CMEDIA_HS100B:
+               if (*rsize == HS100B_RDESC_ORIG_SIZE) {
+                       hid_info(hdev, "Fixing CMedia HS-100B report descriptor\n");
+                       rdesc = hs100b_rdesc_fixed;
+                       *rsize = sizeof(hs100b_rdesc_fixed);
+               }
+               break;
+       }
+       return rdesc;
+}
+
+static const struct hid_device_id cmhid_fixup_devices[] = {
+       { HID_USB_DEVICE(USB_VENDOR_ID_CMEDIA, USB_DEVICE_ID_CMEDIA_HS100B) },
+       { }
+};
+
+static struct hid_driver cmhid_fixup_driver = {
+       .name = "cmedia_fixups",
+       .id_table = cmhid_fixup_devices,
+       .report_fixup = cmhid_fixup_report_fixup,
+};
+module_hid_driver(cmhid_fixup_driver);
+
+MODULE_DEVICE_TABLE(hid, cmhid_fixup_devices);
+MODULE_AUTHOR("Thomas Weißschuh <thomas@weissschuh.net>");
+MODULE_DESCRIPTION("CMedia HID fixup");
+MODULE_LICENSE("GPL");

diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 8f1893e68112..6864e4e6ac8b 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h

@@ -292,6 +292,7 @@

 #define USB_VENDOR_ID_CMEDIA           0x0d8c
 #define USB_DEVICE_ID_CM109            0x000e
+#define USB_DEVICE_ID_CMEDIA_HS100B    0x0014
 #define USB_DEVICE_ID_CM6533           0x0022

 #define USB_VENDOR_ID_CODEMERCS                0x07c0

diff --git a/drivers/hid/hid-quirks.c b/drivers/hid/hid-quirks.c
index 51b39bda9a9d..7776aa13ee27 100644
--- a/drivers/hid/hid-quirks.c
+++ b/drivers/hid/hid-quirks.c

@@ -346,6 +346,9 @@ static const struct hid_device_id hid_have_special_driver[] = {
 #if IS_ENABLED(CONFIG_HID_CMEDIA)
        { HID_USB_DEVICE(USB_VENDOR_ID_CMEDIA, USB_DEVICE_ID_CM6533) },
 #endif
+#if IS_ENABLED(CONFIG_HID_CMEDIA_FIXUP)
+       { HID_USB_DEVICE(USB_VENDOR_ID_CMEDIA, USB_DEVICE_ID_CMEDIA_HS100B) },
+#endif