1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Surface System Aggregator Module (SSAM) HID transport driver for the
4 * generic HID interface (HID/TC=0x15 subsystem). Provides support for
5 * integrated HID devices on Surface Laptop 3, Book 3, and later.
6 *
7 * Copyright (C) 2019-2021 Blaž Hrastnik <blaz@mxxn.io>,
8 * Maximilian Luz <luzmaximilian@gmail.com>
9 */
10
11#include <linux/unaligned.h>
12#include <linux/hid.h>
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/types.h>
16
17#include <linux/surface_aggregator/controller.h>
18#include <linux/surface_aggregator/device.h>
19
20#include "surface_hid_core.h"
21
22
23/* -- SAM interface. -------------------------------------------------------- */
24
25struct surface_hid_buffer_slice {
26 __u8 entry;
27 __le32 offset;
28 __le32 length;
29 __u8 end;
30 __u8 data[];
31} __packed;
32
33static_assert(sizeof(struct surface_hid_buffer_slice) == 10);
34
35enum surface_hid_cid {
36 SURFACE_HID_CID_OUTPUT_REPORT = 0x01,
37 SURFACE_HID_CID_GET_FEATURE_REPORT = 0x02,
38 SURFACE_HID_CID_SET_FEATURE_REPORT = 0x03,
39 SURFACE_HID_CID_GET_DESCRIPTOR = 0x04,
40};
41
42static int ssam_hid_get_descriptor(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len)
43{
44 u8 buffer[sizeof(struct surface_hid_buffer_slice) + 0x76];
45 struct surface_hid_buffer_slice *slice;
46 struct ssam_request rqst;
47 struct ssam_response rsp;
48 u32 buffer_len, offset, length;
49 int status;
50
51 /*
52 * Note: The 0x76 above has been chosen because that's what's used by
53 * the Windows driver. Together with the header, this leads to a 128
54 * byte payload in total.
55 */
56
57 buffer_len = ARRAY_SIZE(buffer) - sizeof(struct surface_hid_buffer_slice);
58
59 rqst.target_category = shid->uid.category;
60 rqst.target_id = shid->uid.target;
61 rqst.command_id = SURFACE_HID_CID_GET_DESCRIPTOR;
62 rqst.instance_id = shid->uid.instance;
63 rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
64 rqst.length = sizeof(struct surface_hid_buffer_slice);
65 rqst.payload = buffer;
66
67 rsp.capacity = ARRAY_SIZE(buffer);
68 rsp.pointer = buffer;
69
70 slice = (struct surface_hid_buffer_slice *)buffer;
71 slice->entry = entry;
72 slice->end = 0;
73
74 offset = 0;
75 length = buffer_len;
76
77 while (!slice->end && offset < len) {
78 put_unaligned_le32(val: offset, p: &slice->offset);
79 put_unaligned_le32(val: length, p: &slice->length);
80
81 rsp.length = 0;
82
83 status = ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp,
84 sizeof(*slice));
85 if (status)
86 return status;
87
88 offset = get_unaligned_le32(p: &slice->offset);
89 length = get_unaligned_le32(p: &slice->length);
90
91 /* Don't mess stuff up in case we receive garbage. */
92 if (length > buffer_len || offset > len)
93 return -EPROTO;
94
95 if (offset + length > len)
96 length = len - offset;
97
98 memcpy(buf + offset, &slice->data[0], length);
99
100 offset += length;
101 length = buffer_len;
102 }
103
104 if (offset != len) {
105 dev_err(shid->dev, "unexpected descriptor length: got %u, expected %zu\n",
106 offset, len);
107 return -EPROTO;
108 }
109
110 return 0;
111}
112
113static int ssam_hid_set_raw_report(struct surface_hid_device *shid, u8 rprt_id, bool feature,
114 u8 *buf, size_t len)
115{
116 struct ssam_request rqst;
117 u8 cid;
118
119 if (feature)
120 cid = SURFACE_HID_CID_SET_FEATURE_REPORT;
121 else
122 cid = SURFACE_HID_CID_OUTPUT_REPORT;
123
124 rqst.target_category = shid->uid.category;
125 rqst.target_id = shid->uid.target;
126 rqst.instance_id = shid->uid.instance;
127 rqst.command_id = cid;
128 rqst.flags = 0;
129 rqst.length = len;
130 rqst.payload = buf;
131
132 buf[0] = rprt_id;
133
134 return ssam_retry(ssam_request_do_sync, shid->ctrl, &rqst, NULL);
135}
136
137static int ssam_hid_get_raw_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
138{
139 struct ssam_request rqst;
140 struct ssam_response rsp;
141
142 rqst.target_category = shid->uid.category;
143 rqst.target_id = shid->uid.target;
144 rqst.instance_id = shid->uid.instance;
145 rqst.command_id = SURFACE_HID_CID_GET_FEATURE_REPORT;
146 rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
147 rqst.length = sizeof(rprt_id);
148 rqst.payload = &rprt_id;
149
150 rsp.capacity = len;
151 rsp.length = 0;
152 rsp.pointer = buf;
153
154 return ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(rprt_id));
155}
156
157static u32 ssam_hid_event_fn(struct ssam_event_notifier *nf, const struct ssam_event *event)
158{
159 struct surface_hid_device *shid = container_of(nf, struct surface_hid_device, notif);
160
161 if (event->command_id != 0x00)
162 return 0;
163
164 hid_input_report(hid: shid->hid, type: HID_INPUT_REPORT, data: (u8 *)&event->data[0], size: event->length, interrupt: 0);
165 return SSAM_NOTIF_HANDLED;
166}
167
168
169/* -- Transport driver. ----------------------------------------------------- */
170
171static int shid_output_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
172{
173 int status;
174
175 status = ssam_hid_set_raw_report(shid, rprt_id, feature: false, buf, len);
176 return status >= 0 ? len : status;
177}
178
179static int shid_get_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
180{
181 int status;
182
183 status = ssam_hid_get_raw_report(shid, rprt_id, buf, len);
184 return status >= 0 ? len : status;
185}
186
187static int shid_set_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
188{
189 int status;
190
191 status = ssam_hid_set_raw_report(shid, rprt_id, feature: true, buf, len);
192 return status >= 0 ? len : status;
193}
194
195
196/* -- Driver setup. --------------------------------------------------------- */
197
198static int surface_hid_probe(struct ssam_device *sdev)
199{
200 struct surface_hid_device *shid;
201
202 shid = devm_kzalloc(dev: &sdev->dev, size: sizeof(*shid), GFP_KERNEL);
203 if (!shid)
204 return -ENOMEM;
205
206 shid->dev = &sdev->dev;
207 shid->ctrl = sdev->ctrl;
208 shid->uid = sdev->uid;
209
210 shid->notif.base.priority = 1;
211 shid->notif.base.fn = ssam_hid_event_fn;
212 shid->notif.event.reg = SSAM_EVENT_REGISTRY_REG(sdev->uid.target);
213 shid->notif.event.id.target_category = sdev->uid.category;
214 shid->notif.event.id.instance = sdev->uid.instance;
215 shid->notif.event.mask = SSAM_EVENT_MASK_STRICT;
216 shid->notif.event.flags = 0;
217
218 shid->ops.get_descriptor = ssam_hid_get_descriptor;
219 shid->ops.output_report = shid_output_report;
220 shid->ops.get_feature_report = shid_get_feature_report;
221 shid->ops.set_feature_report = shid_set_feature_report;
222
223 ssam_device_set_drvdata(sdev, data: shid);
224 return surface_hid_device_add(shid);
225}
226
227static void surface_hid_remove(struct ssam_device *sdev)
228{
229 surface_hid_device_destroy(shid: ssam_device_get_drvdata(sdev));
230}
231
232static const struct ssam_device_id surface_hid_match[] = {
233 { SSAM_SDEV(HID, ANY, SSAM_SSH_IID_ANY, 0x00) },
234 { },
235};
236MODULE_DEVICE_TABLE(ssam, surface_hid_match);
237
238static struct ssam_device_driver surface_hid_driver = {
239 .probe = surface_hid_probe,
240 .remove = surface_hid_remove,
241 .match_table = surface_hid_match,
242 .driver = {
243 .name = "surface_hid",
244 .pm = &surface_hid_pm_ops,
245 .probe_type = PROBE_PREFER_ASYNCHRONOUS,
246 },
247};
248module_ssam_device_driver(surface_hid_driver);
249
250MODULE_AUTHOR("Blaž Hrastnik <blaz@mxxn.io>");
251MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
252MODULE_DESCRIPTION("HID transport driver for Surface System Aggregator Module");
253MODULE_LICENSE("GPL");
254

source code of linux/drivers/hid/surface-hid/surface_hid.c