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Subject[PATCH v2 4/4] HID: core: remove the absolute need of hid_have_special_driver[]
Date
Most HID devices behave properly when they are used with hid-generic.
Since kernel v4.12, we do not poll for input reports at plug in, so
hid-generic should behave properly with all HID devices.

There has been a long standing list of HID devices that have a special
driver. It used to be just a few, but with time, this list went too big,
and we can not ask users to know which HID special driver will pick up
their device.

We can teach hid-generic to be nice with others. If a device is not
explicitly marked with HID_QUIRK_HAVE_SPECIAL_DRIVER, we can allow
hid-generic to pick up the device as long as no other loaded HID driver
will match the device.

When the special driver appears, hid-generic can step back and let
the special driver handling the device. In case this special driver
is removed, this good old pal of hid-generic will rebind to the device.

This basically makes the list hid_have_special_driver[] useless. It
still allows to not see a hid-generic driver bound and removed during
boot, so we can keep it around.

This will also help other people to have a special HID driver without
the need of recompiling hid-core.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

---
no changes in v2
---
drivers/hid/hid-core.c | 76 ++++++++++++++++++++++++++++++-----------------
drivers/hid/hid-generic.c | 68 +++++++++++++++++++++++++++++++++++++++++-
include/linux/hid.h | 10 +++++++
3 files changed, 125 insertions(+), 29 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index e6d586a..7297b1d 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -830,31 +830,6 @@ static int hid_scan_report(struct hid_device *hid)
break;
}

- /* fall back to generic driver in case specific driver doesn't exist */
- switch (hid->group) {
- case HID_GROUP_MULTITOUCH_WIN_8:
- /* fall-through */
- case HID_GROUP_MULTITOUCH:
- if (!IS_ENABLED(CONFIG_HID_MULTITOUCH))
- hid->group = HID_GROUP_GENERIC;
- break;
- case HID_GROUP_SENSOR_HUB:
- if (!IS_ENABLED(CONFIG_HID_SENSOR_HUB))
- hid->group = HID_GROUP_GENERIC;
- break;
- case HID_GROUP_RMI:
- if (!IS_ENABLED(CONFIG_HID_RMI))
- hid->group = HID_GROUP_GENERIC;
- break;
- case HID_GROUP_WACOM:
- if (!IS_ENABLED(CONFIG_HID_WACOM))
- hid->group = HID_GROUP_GENERIC;
- break;
- case HID_GROUP_LOGITECH_DJ_DEVICE:
- if (!IS_ENABLED(CONFIG_HID_LOGITECH_DJ))
- hid->group = HID_GROUP_GENERIC;
- break;
- }
vfree(parser);
return 0;
}
@@ -1928,8 +1903,8 @@ static void hid_free_dynids(struct hid_driver *hdrv)
spin_unlock(&hdrv->dyn_lock);
}

-static const struct hid_device_id *hid_match_device(struct hid_device *hdev,
- struct hid_driver *hdrv)
+const struct hid_device_id *hid_match_device(struct hid_device *hdev,
+ struct hid_driver *hdrv)
{
struct hid_dynid *dynid;

@@ -1944,6 +1919,7 @@ static const struct hid_device_id *hid_match_device(struct hid_device *hdev,

return hid_match_id(hdev, hdrv->id_table);
}
+EXPORT_SYMBOL_GPL(hid_match_device);

static int hid_bus_match(struct device *dev, struct device_driver *drv)
{
@@ -1973,6 +1949,23 @@ static int hid_device_probe(struct device *dev)
goto unlock;
}

+ if (hdrv->match) {
+ if (!hdrv->match(hdev, hid_ignore_special_drivers)) {
+ ret = -ENODEV;
+ goto unlock;
+ }
+ } else {
+ /*
+ * hid-generic implements .match(), so if
+ * hid_ignore_special_drivers is set, we can safely
+ * return.
+ */
+ if (hid_ignore_special_drivers) {
+ ret = -ENODEV;
+ goto unlock;
+ }
+ }
+
hdev->driver = hdrv;
if (hdrv->probe) {
ret = hdrv->probe(hdev, id);
@@ -2069,7 +2062,7 @@ static int hid_uevent(struct device *dev, struct kobj_uevent_env *env)
return 0;
}

-static struct bus_type hid_bus_type = {
+struct bus_type hid_bus_type = {
.name = "hid",
.dev_groups = hid_dev_groups,
.drv_groups = hid_drv_groups,
@@ -2203,6 +2196,29 @@ void hid_destroy_device(struct hid_device *hdev)
}
EXPORT_SYMBOL_GPL(hid_destroy_device);

+
+static int __bus_add_driver(struct device_driver *drv, void *data)
+{
+ struct hid_driver *added_hdrv = data;
+ struct hid_driver *hdrv = to_hid_driver(drv);
+
+ if (hdrv->bus_add_driver)
+ hdrv->bus_add_driver(added_hdrv);
+
+ return 0;
+}
+
+static int __bus_removed_driver(struct device_driver *drv, void *data)
+{
+ struct hid_driver *removed_hdrv = data;
+ struct hid_driver *hdrv = to_hid_driver(drv);
+
+ if (hdrv->bus_removed_driver)
+ hdrv->bus_removed_driver(removed_hdrv);
+
+ return 0;
+}
+
int __hid_register_driver(struct hid_driver *hdrv, struct module *owner,
const char *mod_name)
{
@@ -2214,6 +2230,8 @@ int __hid_register_driver(struct hid_driver *hdrv, struct module *owner,
INIT_LIST_HEAD(&hdrv->dyn_list);
spin_lock_init(&hdrv->dyn_lock);

+ bus_for_each_drv(&hid_bus_type, NULL, hdrv, __bus_add_driver);
+
return driver_register(&hdrv->driver);
}
EXPORT_SYMBOL_GPL(__hid_register_driver);
@@ -2222,6 +2240,8 @@ void hid_unregister_driver(struct hid_driver *hdrv)
{
driver_unregister(&hdrv->driver);
hid_free_dynids(hdrv);
+
+ bus_for_each_drv(&hid_bus_type, NULL, hdrv, __bus_removed_driver);
}
EXPORT_SYMBOL_GPL(hid_unregister_driver);

diff --git a/drivers/hid/hid-generic.c b/drivers/hid/hid-generic.c
index e288a4a..3c0a1bf 100644
--- a/drivers/hid/hid-generic.c
+++ b/drivers/hid/hid-generic.c
@@ -24,8 +24,71 @@

#include <linux/hid.h>

+static struct hid_driver hid_generic;
+
+static int __unmap_hid_generic(struct device *dev, void *data)
+{
+ struct hid_driver *hdrv = data;
+ struct hid_device *hdev = to_hid_device(dev);
+
+ /* only unbind matching devices already bound to hid-generic */
+ if (hdev->driver != &hid_generic ||
+ hid_match_device(hdev, hdrv) == NULL)
+ return 0;
+
+ if (dev->parent) /* Needed for USB */
+ device_lock(dev->parent);
+ device_release_driver(dev);
+ if (dev->parent)
+ device_unlock(dev->parent);
+
+ return 0;
+}
+
+static void hid_generic_add_driver(struct hid_driver *hdrv)
+{
+ bus_for_each_dev(&hid_bus_type, NULL, hdrv, __unmap_hid_generic);
+}
+
+static void hid_generic_removed_driver(struct hid_driver *hdrv)
+{
+ int ret;
+
+ ret = driver_attach(&hid_generic.driver);
+}
+
+static int __check_hid_generic(struct device_driver *drv, void *data)
+{
+ struct hid_driver *hdrv = to_hid_driver(drv);
+ struct hid_device *hdev = data;
+
+ if (hdrv == &hid_generic)
+ return 0;
+
+ return hid_match_device(hdev, hdrv) != NULL;
+}
+
+static bool hid_generic_match(struct hid_device *hdev,
+ bool ignore_special_driver)
+{
+ if (ignore_special_driver)
+ return true;
+
+ if (hdev->quirks & HID_QUIRK_HAVE_SPECIAL_DRIVER)
+ return false;
+
+ /*
+ * If any other driver wants the device, leave the device to this other
+ * driver.
+ */
+ if (bus_for_each_drv(&hid_bus_type, NULL, hdev, __check_hid_generic))
+ return false;
+
+ return true;
+}
+
static const struct hid_device_id hid_table[] = {
- { HID_DEVICE(HID_BUS_ANY, HID_GROUP_GENERIC, HID_ANY_ID, HID_ANY_ID) },
+ { HID_DEVICE(HID_BUS_ANY, HID_GROUP_ANY, HID_ANY_ID, HID_ANY_ID) },
{ }
};
MODULE_DEVICE_TABLE(hid, hid_table);
@@ -33,6 +96,9 @@ MODULE_DEVICE_TABLE(hid, hid_table);
static struct hid_driver hid_generic = {
.name = "hid-generic",
.id_table = hid_table,
+ .match = hid_generic_match,
+ .bus_add_driver = hid_generic_add_driver,
+ .bus_removed_driver = hid_generic_removed_driver,
};
module_hid_driver(hid_generic);

diff --git a/include/linux/hid.h b/include/linux/hid.h
index 6ba8d21..8336774 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -671,6 +671,7 @@ struct hid_usage_id {
* to be called)
* @dyn_list: list of dynamically added device ids
* @dyn_lock: lock protecting @dyn_list
+ * @match: check if the given device is handled by this driver
* @probe: new device inserted
* @remove: device removed (NULL if not a hot-plug capable driver)
* @report_table: on which reports to call raw_event (NULL means all)
@@ -683,6 +684,8 @@ struct hid_usage_id {
* @input_mapped: invoked on input registering after mapping an usage
* @input_configured: invoked just before the device is registered
* @feature_mapping: invoked on feature registering
+ * @bus_add_driver: invoked when a HID driver is about to be added
+ * @bus_removed_driver: invoked when a HID driver has been removed
* @suspend: invoked on suspend (NULL means nop)
* @resume: invoked on resume if device was not reset (NULL means nop)
* @reset_resume: invoked on resume if device was reset (NULL means nop)
@@ -711,6 +714,7 @@ struct hid_driver {
struct list_head dyn_list;
spinlock_t dyn_lock;

+ bool (*match)(struct hid_device *dev, bool ignore_special_driver);
int (*probe)(struct hid_device *dev, const struct hid_device_id *id);
void (*remove)(struct hid_device *dev);

@@ -736,6 +740,8 @@ struct hid_driver {
void (*feature_mapping)(struct hid_device *hdev,
struct hid_field *field,
struct hid_usage *usage);
+ void (*bus_add_driver)(struct hid_driver *driver);
+ void (*bus_removed_driver)(struct hid_driver *driver);
#ifdef CONFIG_PM
int (*suspend)(struct hid_device *hdev, pm_message_t message);
int (*resume)(struct hid_device *hdev);
@@ -814,6 +820,8 @@ extern bool hid_ignore(struct hid_device *);
extern int hid_add_device(struct hid_device *);
extern void hid_destroy_device(struct hid_device *);

+extern struct bus_type hid_bus_type;
+
extern int __must_check __hid_register_driver(struct hid_driver *,
struct module *, const char *mod_name);

@@ -864,6 +872,8 @@ bool hid_match_one_id(const struct hid_device *hdev,
const struct hid_device_id *id);
const struct hid_device_id *hid_match_id(const struct hid_device *hdev,
const struct hid_device_id *id);
+const struct hid_device_id *hid_match_device(struct hid_device *hdev,
+ struct hid_driver *hdrv);
s32 hid_snto32(__u32 value, unsigned n);
__u32 hid_field_extract(const struct hid_device *hid, __u8 *report,
unsigned offset, unsigned n);
--
2.9.5
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