The use case is when we fix a device through HID-BPF, 99% of the cases we want the device to use hid-generic now instead of a dedicated device.
That's because the dedicated device might also want to change the report descriptor, or will be handling the device in a different way the new fixed device is using. In hid-core, after matching for the device (so that we only call this new hook on compatible drivers), we call for `.hid_bpf_driver_probe`. The function can not communicate with the device because it is not yet started, but it can make educated guesses and decide to: - let hid-core decide by itself - force the use of this driver (by comparing the provided name with "hid-generic" for instance) - force hid-core to ignore this driver for this device. For API stability, we don't rely on a bitfield or a return value for chosing hid-core behavior. We simply have a couple of writeable fields in the new struct hid_bpf_driver, and then hid-core can make its educated decision. Signed-off-by: Benjamin Tissoires <[email protected]> --- Documentation/hid/hid-bpf.rst | 2 +- drivers/hid/bpf/hid_bpf_dispatch.c | 31 ++++++++++++++++++++++++++++ drivers/hid/bpf/hid_bpf_struct_ops.c | 3 +++ drivers/hid/hid-core.c | 6 ++++++ include/linux/hid_bpf.h | 40 ++++++++++++++++++++++++++++++++++++ 5 files changed, 81 insertions(+), 1 deletion(-) diff --git a/Documentation/hid/hid-bpf.rst b/Documentation/hid/hid-bpf.rst index 5939eeafb361..05a43f11cdab 100644 --- a/Documentation/hid/hid-bpf.rst +++ b/Documentation/hid/hid-bpf.rst @@ -190,7 +190,7 @@ User API data structures available in programs: ----------------------------------------------- .. kernel-doc:: include/linux/hid_bpf.h - :identifiers: hid_bpf_ctx + :identifiers: hid_bpf_ctx hid_bpf_driver Available API that can be used in all HID-BPF struct_ops programs: ------------------------------------------------------------------ diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c index a272a086c950..2df136d64152 100644 --- a/drivers/hid/bpf/hid_bpf_dispatch.c +++ b/drivers/hid/bpf/hid_bpf_dispatch.c @@ -189,6 +189,37 @@ u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *s } EXPORT_SYMBOL_GPL(call_hid_bpf_rdesc_fixup); +int call_hid_bpf_driver_probe(struct hid_device *hdev, struct hid_driver *hdrv, + const struct hid_device_id *id) +{ + struct hid_bpf_driver drv = { 0 }; + struct hid_bpf_ops *e; + int idx; + + if (strscpy(drv.name, hdrv->name, sizeof(drv.name)) < 0) + return 0; + + idx = srcu_read_lock(&hdev->bpf.srcu); + list_for_each_entry_srcu(e, &hdev->bpf.prog_list, list, + srcu_read_lock_held(&hdev->bpf.srcu)) { + if (!e->hid_driver_probe) + continue; + + e->hid_driver_probe(hdev, &drv, id); + } + + srcu_read_unlock(&hdev->bpf.srcu, idx); + + if (drv.force_driver) + return 1; + + if (drv.ignore_driver) + return -1; + + return 0; +} +EXPORT_SYMBOL_GPL(call_hid_bpf_driver_probe); + static int device_match_id(struct device *dev, const void *id) { struct hid_device *hdev = to_hid_device(dev); diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c index cd696c59ba0f..1e13a22f73a1 100644 --- a/drivers/hid/bpf/hid_bpf_struct_ops.c +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c @@ -46,6 +46,7 @@ static int hid_bpf_ops_check_member(const struct btf_type *t, case offsetof(struct hid_bpf_ops, hid_rdesc_fixup): case offsetof(struct hid_bpf_ops, hid_hw_request): case offsetof(struct hid_bpf_ops, hid_hw_output_report): + case offsetof(struct hid_bpf_ops, hid_driver_probe): break; default: if (prog->sleepable) @@ -79,6 +80,8 @@ static int hid_bpf_ops_btf_struct_access(struct bpf_verifier_log *log, WRITE_RANGE(hid_device, name, true), WRITE_RANGE(hid_device, uniq, true), WRITE_RANGE(hid_device, phys, true), + WRITE_RANGE(hid_bpf_driver, force_driver, false), + WRITE_RANGE(hid_bpf_driver, ignore_driver, false), }; #undef WRITE_RANGE const struct btf_type *state = NULL; diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 988d0acbdf04..7845f0a789ec 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -2639,10 +2639,16 @@ static bool hid_check_device_match(struct hid_device *hdev, struct hid_driver *hdrv, const struct hid_device_id **id) { + int ret; + *id = hid_match_device(hdev, hdrv); if (!*id) return false; + ret = call_hid_bpf_driver_probe(hdev, hdrv, *id); + if (ret) + return ret > 0; + if (hdrv->match) return hdrv->match(hdev, hid_ignore_special_drivers); diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h index d4d063cf63b5..20693c218857 100644 --- a/include/linux/hid_bpf.h +++ b/include/linux/hid_bpf.h @@ -9,6 +9,7 @@ #include <uapi/linux/hid.h> struct hid_device; +struct hid_driver; /* * The following is the user facing HID BPF API. @@ -80,6 +81,22 @@ struct hid_ops { extern struct hid_ops *hid_ops; +/** + * struct hid_bpf_driver - User accessible data for the ``hid_bpf_probe`` + * struct_ops + * + * @name: the name of the driver currently being treated + * @force_driver: set this to ``true`` to force hid-core to use this driver, + * bypassing any further decision made by this driver + * @ignore_driver: set this to ``true`` to force hid-core to ignore this driver, + * bypassing any further decision made by this driver + */ +struct hid_bpf_driver { + __u8 name[64]; + bool force_driver; + bool ignore_driver; +}; + /** * struct hid_bpf_ops - A BPF struct_ops of callbacks allowing to attach HID-BPF * programs to a HID device @@ -178,6 +195,25 @@ struct hid_bpf_ops { */ int (*hid_hw_output_report)(struct hid_bpf_ctx *ctx, u64 source); + /** + * @hid_driver_probe: called before the kernel ``.probe()`` function + * + * It has the following arguments: + * + * ``hdev``: The HID device kernel representation + * + * ``hdrv``: A BPF partially writeable representation of a HID driver + * + * ``id``: The device match structure found in the driver + * + * Note that the device has not been started yet, and thus kfuncs like + * ``hid_hw_output_report`` will likely fail. + * + * This function is useful to force/ignore a given supported HID driver, + * by writing ``true`` in ``hdrv->force_driver`` or ``hdrv->ignore_driver`` + */ + void (*hid_driver_probe)(struct hid_device *hdev, struct hid_bpf_driver *hdrv, + const struct hid_device_id *id); /* private: do not show up in the docs */ struct hid_device *hdev; @@ -213,6 +249,8 @@ void hid_bpf_disconnect_device(struct hid_device *hdev); void hid_bpf_destroy_device(struct hid_device *hid); int hid_bpf_device_init(struct hid_device *hid); u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size); +int call_hid_bpf_driver_probe(struct hid_device *hdev, struct hid_driver *hdrv, + const struct hid_device_id *id); #else /* CONFIG_HID_BPF */ static inline u8 *dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type, u8 *data, u32 *size, int interrupt, @@ -228,6 +266,8 @@ static inline int hid_bpf_connect_device(struct hid_device *hdev) { return 0; } static inline void hid_bpf_disconnect_device(struct hid_device *hdev) {} static inline void hid_bpf_destroy_device(struct hid_device *hid) {} static inline int hid_bpf_device_init(struct hid_device *hid) { return 0; } +static inline int call_hid_bpf_driver_probe(struct hid_device *hdev, struct hid_driver *hdrv, + const struct hid_device_id *id) { return 0; } /* * This specialized allocator has to be a macro for its allocations to be * accounted separately (to have a separate alloc_tag). The typecast is -- 2.46.0
