// SPDX-License-Identifier: GPL-2.0+
/*
* Surface System Aggregator Module (SSAM) HID transport driver for the
* generic HID interface (HID/TC=0x15 subsystem). Provides support for
* integrated HID devices on Surface Laptop 3, Book 3, and later.
*
* Copyright (C) 2019-2021 Blaž Hrastnik <[email protected]>,
* Maximilian Luz <[email protected]>
*/
#include <linux/unaligned.h>
#include <linux/hid.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/surface_aggregator/controller.h>
#include <linux/surface_aggregator/device.h>
#include "surface_hid_core.h"
/* -- SAM interface. -------------------------------------------------------- */
struct surface_hid_buffer_slice {
__u8 entry;
__le32 offset;
__le32 length;
__u8 end;
__u8 data[];
} __packed;
static_assert(sizeof(struct surface_hid_buffer_slice) == 10);
enum surface_hid_cid {
SURFACE_HID_CID_OUTPUT_REPORT = 0x01,
SURFACE_HID_CID_GET_FEATURE_REPORT = 0x02,
SURFACE_HID_CID_SET_FEATURE_REPORT = 0x03,
SURFACE_HID_CID_GET_DESCRIPTOR = 0x04,
};
static int ssam_hid_get_descriptor(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len)
{
u8 buffer[sizeof(struct surface_hid_buffer_slice) + 0x76];
struct surface_hid_buffer_slice *slice;
struct ssam_request rqst;
struct ssam_response rsp;
u32 buffer_len, offset, length;
int status;
/*
* Note: The 0x76 above has been chosen because that's what's used by
* the Windows driver. Together with the header, this leads to a 128
* byte payload in total.
*/
buffer_len = ARRAY_SIZE(buffer) - sizeof(struct surface_hid_buffer_slice);
rqst.target_category = shid->uid.category;
rqst.target_id = shid->uid.target;
rqst.command_id = SURFACE_HID_CID_GET_DESCRIPTOR;
rqst.instance_id = shid->uid.instance;
rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
rqst.length = sizeof(struct surface_hid_buffer_slice);
rqst.payload = buffer;
rsp.capacity = ARRAY_SIZE(buffer);
rsp.pointer = buffer;
slice = (struct surface_hid_buffer_slice *)buffer;
slice->entry = entry;
slice->end = 0;
offset = 0;
length = buffer_len;
while (!slice->end && offset < len) {
put_unaligned_le32(offset, &slice->offset);
put_unaligned_le32(length, &slice->length);
rsp.length = 0;
status = ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp,
sizeof(*slice));
if (status)
return status;
offset = get_unaligned_le32(&slice->offset);
length = get_unaligned_le32(&slice->length);
/* Don't mess stuff up in case we receive garbage. */
if (length > buffer_len || offset > len)
return -EPROTO;
if (offset + length > len)
length = len - offset;
memcpy(buf + offset, &slice->data[0], length);
offset += length;
length = buffer_len;
}
if (offset != len) {
dev_err(shid->dev, "unexpected descriptor length: got %u, expected %zu\n",
offset, len);
return -EPROTO;
}
return 0;
}
static int ssam_hid_set_raw_report(struct surface_hid_device *shid, u8 rprt_id, bool feature,
u8 *buf, size_t len)
{
struct ssam_request rqst;
u8 cid;
if (feature)
cid = SURFACE_HID_CID_SET_FEATURE_REPORT;
else
cid = SURFACE_HID_CID_OUTPUT_REPORT;
rqst.target_category = shid->uid.category;
rqst.target_id = shid->uid.target;
rqst.instance_id = shid->uid.instance;
rqst.command_id = cid;
rqst.flags = 0;
rqst.length = len;
rqst.payload = buf;
buf[0] = rprt_id;
return ssam_retry(ssam_request_do_sync, shid->ctrl, &rqst, NULL);
}
static int ssam_hid_get_raw_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
{
struct ssam_request rqst;
struct ssam_response rsp;
rqst.target_category = shid->uid.category;
rqst.target_id = shid->uid.target;
rqst.instance_id = shid->uid.instance;
rqst.command_id = SURFACE_HID_CID_GET_FEATURE_REPORT;
rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
rqst.length = sizeof(rprt_id);
rqst.payload = &rprt_id;
rsp.capacity = len;
rsp.length = 0;
rsp.pointer = buf;
return ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(rprt_id));
}
static u32 ssam_hid_event_fn(struct ssam_event_notifier *nf, const struct ssam_event *event)
{
struct surface_hid_device *shid = container_of(nf, struct surface_hid_device, notif);
if (event->command_id != 0x00)
return 0;
hid_input_report(shid->hid, HID_INPUT_REPORT, (u8 *)&event->data[0], event->length, 0);
return SSAM_NOTIF_HANDLED;
}
/* -- Transport driver. ----------------------------------------------------- */
static int shid_output_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
{
int status;
status = ssam_hid_set_raw_report(shid, rprt_id, false, buf, len);
return status >= 0 ? len : status;
}
static int shid_get_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
{
int status;
status = ssam_hid_get_raw_report(shid, rprt_id, buf, len);
return status >= 0 ? len : status;
}
static int shid_set_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
{
int status;
status = ssam_hid_set_raw_report(shid, rprt_id, true, buf, len);
return status >= 0 ? len : status;
}
/* -- Driver setup. --------------------------------------------------------- */
static int surface_hid_probe(struct ssam_device *sdev)
{
struct surface_hid_device *shid;
shid = devm_kzalloc(&sdev->dev, sizeof(*shid), GFP_KERNEL);
if (!shid)
return -ENOMEM;
shid->dev = &sdev->dev;
shid->ctrl = sdev->ctrl;
shid->uid = sdev->uid;
shid->notif.base.priority = 1;
shid->notif.base.fn = ssam_hid_event_fn;
shid->notif.event.reg = SSAM_EVENT_REGISTRY_REG(sdev->uid.target);
shid->notif.event.id.target_category = sdev->uid.category;
shid->notif.event.id.instance = sdev->uid.instance;
shid->notif.event.mask = SSAM_EVENT_MASK_STRICT;
shid->notif.event.flags = 0;
shid->ops.get_descriptor = ssam_hid_get_descriptor;
shid->ops.output_report = shid_output_report;
shid->ops.get_feature_report = shid_get_feature_report;
shid->ops.set_feature_report = shid_set_feature_report;
ssam_device_set_drvdata(sdev, shid);
return surface_hid_device_add(shid);
}
static void surface_hid_remove(struct ssam_device *sdev)
{
surface_hid_device_destroy(ssam_device_get_drvdata(sdev));
}
static const struct ssam_device_id surface_hid_match[] = {
{ SSAM_SDEV(HID, ANY, SSAM_SSH_IID_ANY, 0x00) },
{ },
};
MODULE_DEVICE_TABLE(ssam, surface_hid_match);
static struct ssam_device_driver surface_hid_driver = {
.probe = surface_hid_probe,
.remove = surface_hid_remove,
.match_table = surface_hid_match,
.driver = {
.name = "surface_hid",
.pm = &surface_hid_pm_ops,
.probe_type = PROBE_PREFER_ASYNCHRONOUS,
},
};
module_ssam_device_driver(surface_hid_driver);
MODULE_AUTHOR("Blaž Hrastnik <[email protected]>");
MODULE_AUTHOR("Maximilian Luz <[email protected]>");
MODULE_DESCRIPTION("HID transport driver for Surface System Aggregator Module");
MODULE_LICENSE("GPL");
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