[PATCH for-5.19/uclogic v2 0/4] Add support for XP-PEN Deco L

[PATCH for-5.19/uclogic v2 0/4] Add support for XP-PEN Deco L

[José Expósito]

Hello everyone,

This patchset adds support for the UGEE XP-PEN Deco L tablet.
This device belongs to a family of tablets that must receive a chunk of
magic data in order to be enabled (named UGEE v2 internally).

Once the device is enabled, its parameters can be discovered by parsing
a report descriptor. HUION v1 tablets have a similar report descriptor
but, in the case of UGEE v2 tablets, the number of buttons are also
discoverable [1].

The ability to discover the number of buttons is the reason for the
first 3 patches. They enable frame templates.
Because I lack the hardware to fully test this driver, I added some
KUnit tests to make sure no bugs are introduced.
I didn't see any other test in the subsystem (and I doubt I'm the first
person writing one) so please let me know if I need to move the test to
a different place.

The last patch enables the tablet and it should give Stefan a stable
code to work on his XP-PEN Deco Mini 7 tablet.

Stefan: I didn't include the code for the Mini 4 because once connected
no events are received until I unload and load the driver.
If anyone has a clue about why this could happen, I'd really appreciate
some help. [2]

Best wishes,
José Expósito

[1] I don't own a HUION v1 device, so I'm not sure if the information
    about the number of buttons is also present and it is not used in
    the driver for some reason.
[2] https://lore.kernel.org/linux-input/20220516112159.GA74406@elementary/T/#t

---

v2 - Fix some errors reported by the kernel test robot:

 - Add MODULE_DESCRIPTION/LICENSE/AUTHOR to hid-uclogic-rdesc-test.c
 - Remove unused variable in uclogic_params_ugee_v2_init
 - Add sparse __force anotation in the result of cpu_to_le16
 - Add DISABLE_STRUCTLEAK_PLUGIN for KUnit tests


José Expósito (4):
  HID: uclogic: Make template placeholder IDs generic
  HID: uclogic: Add KUnit tests for uclogic_rdesc_template_apply()
  HID: uclogic: Allow to generate frame templates
  HID: uclogic: Add support for XP-PEN Deco L

 drivers/hid/Kconfig                  |   7 +
 drivers/hid/Makefile                 |   3 +
 drivers/hid/hid-ids.h                |   1 +
 drivers/hid/hid-uclogic-core.c       |   2 +
 drivers/hid/hid-uclogic-params.c     | 201 +++++++++++++++++++++++-
 drivers/hid/hid-uclogic-rdesc-test.c | 219 +++++++++++++++++++++++++++
 drivers/hid/hid-uclogic-rdesc.c      | 124 ++++++++++++++-
 drivers/hid/hid-uclogic-rdesc.h      |  24 ++-
 8 files changed, 567 insertions(+), 14 deletions(-)
 create mode 100644 drivers/hid/hid-uclogic-rdesc-test.c


base-commit: f7d8e387d9aeff963e6691c0166269b8042b4ff9
-- 
2.25.1

[PATCH for-5.19/uclogic v2 1/4] HID: uclogic: Make template placeholder IDs generic

[José Expósito]

Up until now, the report descriptor template parameter IDs were only
used with pen report descriptors and they were named accordingly.

Rename the enum and the total number of IDs to make them interface
agnostic.

Refactor, no functional changes.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
---
 drivers/hid/hid-uclogic-params.c |  4 ++--
 drivers/hid/hid-uclogic-rdesc.c  | 14 +++++++-------
 drivers/hid/hid-uclogic-rdesc.h  | 10 +++++-----
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/hid/hid-uclogic-params.c b/drivers/hid/hid-uclogic-params.c
index db838f16282d..b43142f98a8b 100644
--- a/drivers/hid/hid-uclogic-params.c
+++ b/drivers/hid/hid-uclogic-params.c
@@ -234,7 +234,7 @@ static int uclogic_params_pen_init_v1(struct uclogic_params_pen *pen,
 	const int len = 12;
 	s32 resolution;
 	/* Pen report descriptor template parameters */
-	s32 desc_params[UCLOGIC_RDESC_PEN_PH_ID_NUM];
+	s32 desc_params[UCLOGIC_RDESC_PH_ID_NUM];
 	__u8 *desc_ptr = NULL;
 
 	/* Check arguments */
@@ -379,7 +379,7 @@ static int uclogic_params_pen_init_v2(struct uclogic_params_pen *pen,
 	size_t i;
 	s32 resolution;
 	/* Pen report descriptor template parameters */
-	s32 desc_params[UCLOGIC_RDESC_PEN_PH_ID_NUM];
+	s32 desc_params[UCLOGIC_RDESC_PH_ID_NUM];
 	__u8 *desc_ptr = NULL;
 
 	/* Check arguments */
diff --git a/drivers/hid/hid-uclogic-rdesc.c b/drivers/hid/hid-uclogic-rdesc.c
index 13f9ce73f1b1..7126fba80968 100644
--- a/drivers/hid/hid-uclogic-rdesc.c
+++ b/drivers/hid/hid-uclogic-rdesc.c
@@ -979,7 +979,7 @@ const size_t uclogic_rdesc_xppen_deco01_frame_size =
  * uclogic_rdesc_template_apply() - apply report descriptor parameters to a
  * report descriptor template, creating a report descriptor. Copies the
  * template over to the new report descriptor and replaces every occurrence of
- * UCLOGIC_RDESC_PH_HEAD, followed by an index byte, with the value from the
+ * UCLOGIC_RDESC_PEN_PH_HEAD, followed by an index byte, with the value from the
  * parameter list at that index.
  *
  * @template_ptr:	Pointer to the template buffer.
@@ -996,7 +996,7 @@ __u8 *uclogic_rdesc_template_apply(const __u8 *template_ptr,
 				   const s32 *param_list,
 				   size_t param_num)
 {
-	static const __u8 head[] = {UCLOGIC_RDESC_PH_HEAD};
+	static const __u8 pen_head[] = {UCLOGIC_RDESC_PEN_PH_HEAD};
 	__u8 *rdesc_ptr;
 	__u8 *p;
 	s32 v;
@@ -1005,12 +1005,12 @@ __u8 *uclogic_rdesc_template_apply(const __u8 *template_ptr,
 	if (rdesc_ptr == NULL)
 		return NULL;
 
-	for (p = rdesc_ptr; p + sizeof(head) < rdesc_ptr + template_size;) {
-		if (memcmp(p, head, sizeof(head)) == 0 &&
-		    p[sizeof(head)] < param_num) {
-			v = param_list[p[sizeof(head)]];
+	for (p = rdesc_ptr; p + sizeof(pen_head) < rdesc_ptr + template_size;) {
+		if (memcmp(p, pen_head, sizeof(pen_head)) == 0 &&
+		    p[sizeof(pen_head)] < param_num) {
+			v = param_list[p[sizeof(pen_head)]];
 			put_unaligned(cpu_to_le32(v), (s32 *)p);
-			p += sizeof(head) + 1;
+			p += sizeof(pen_head) + 1;
 		} else {
 			p++;
 		}
diff --git a/drivers/hid/hid-uclogic-rdesc.h b/drivers/hid/hid-uclogic-rdesc.h
index 0c6e95e8bde7..9d37090c39d1 100644
--- a/drivers/hid/hid-uclogic-rdesc.h
+++ b/drivers/hid/hid-uclogic-rdesc.h
@@ -81,7 +81,7 @@ extern __u8 uclogic_rdesc_twha60_fixed1_arr[];
 extern const size_t uclogic_rdesc_twha60_fixed1_size;
 
 /* Report descriptor template placeholder head */
-#define UCLOGIC_RDESC_PH_HEAD	0xFE, 0xED, 0x1D
+#define UCLOGIC_RDESC_PEN_PH_HEAD	0xFE, 0xED, 0x1D
 
 /* Apply report descriptor parameters to a report descriptor template */
 extern __u8 *uclogic_rdesc_template_apply(const __u8 *template_ptr,
@@ -89,19 +89,19 @@ extern __u8 *uclogic_rdesc_template_apply(const __u8 *template_ptr,
 					  const s32 *param_list,
 					  size_t param_num);
 
-/* Pen report descriptor template placeholder IDs */
-enum uclogic_rdesc_pen_ph_id {
+/* Report descriptor template placeholder IDs */
+enum uclogic_rdesc_ph_id {
 	UCLOGIC_RDESC_PEN_PH_ID_X_LM,
 	UCLOGIC_RDESC_PEN_PH_ID_X_PM,
 	UCLOGIC_RDESC_PEN_PH_ID_Y_LM,
 	UCLOGIC_RDESC_PEN_PH_ID_Y_PM,
 	UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM,
-	UCLOGIC_RDESC_PEN_PH_ID_NUM
+	UCLOGIC_RDESC_PH_ID_NUM
 };
 
 /* Report descriptor pen template placeholder */
 #define UCLOGIC_RDESC_PEN_PH(_ID) \
-	UCLOGIC_RDESC_PH_HEAD, UCLOGIC_RDESC_PEN_PH_ID_##_ID
+	UCLOGIC_RDESC_PEN_PH_HEAD, UCLOGIC_RDESC_PEN_PH_ID_##_ID
 
 /* Report ID for v1 pen reports */
 #define UCLOGIC_RDESC_V1_PEN_ID	0x07
-- 
2.25.1

[PATCH for-5.19/uclogic v2 2/4] HID: uclogic: Add KUnit tests for uclogic_rdesc_template_apply()

[José Expósito]

The uclogic_rdesc_template_apply() function is used by the driver to
generate HID descriptors from templates.

In order to avoid regressions in future patches, add KUnit tests to
test the function.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
---
 drivers/hid/Kconfig                  |   7 +
 drivers/hid/Makefile                 |   3 +
 drivers/hid/hid-uclogic-rdesc-test.c | 183 +++++++++++++++++++++++++++
 3 files changed, 193 insertions(+)
 create mode 100644 drivers/hid/hid-uclogic-rdesc-test.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 7a674873d794..2b8dc4c298e6 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -458,6 +458,13 @@ config HID_UCLOGIC
 	help
 	Support for UC-Logic and Huion tablets.
 
+config HID_UCLOGIC_KUNIT_TEST
+	bool "UC-Logic tests" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  KUnit tests for the UC-Logic driver.
+
 config HID_WALTOP
 	tristate "Waltop"
 	depends on HID
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index d5ce8d747b14..3d5ec603d4e6 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -127,6 +127,9 @@ hid-uclogic-objs		:= hid-uclogic-core.o \
 				   hid-uclogic-rdesc.o \
 				   hid-uclogic-params.o
 obj-$(CONFIG_HID_UCLOGIC)	+= hid-uclogic.o
+obj-$(CONFIG_HID_UCLOGIC_KUNIT_TEST)	+= hid-uclogic-rdesc.o \
+					   hid-uclogic-rdesc-test.o
+CFLAGS_hid-uclogic-rdesc-test.o += $(DISABLE_STRUCTLEAK_PLUGIN)
 obj-$(CONFIG_HID_UDRAW_PS3)	+= hid-udraw-ps3.o
 obj-$(CONFIG_HID_LED)		+= hid-led.o
 obj-$(CONFIG_HID_XIAOMI)	+= hid-xiaomi.o
diff --git a/drivers/hid/hid-uclogic-rdesc-test.c b/drivers/hid/hid-uclogic-rdesc-test.c
new file mode 100644
index 000000000000..ded59e226230
--- /dev/null
+++ b/drivers/hid/hid-uclogic-rdesc-test.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ *  HID driver for UC-Logic devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2022 José Expósito <jose.exposito89@gmail.com>
+ */
+
+#include <kunit/test.h>
+#include "./hid-uclogic-rdesc.h"
+
+struct uclogic_template_case {
+	const char *name;
+	const __u8 *template;
+	size_t template_size;
+	const s32 *param_list;
+	size_t param_num;
+	const __u8 *expected;
+};
+
+static const s32 params_pen_all[UCLOGIC_RDESC_PH_ID_NUM] = {
+	[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xAA,
+	[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0xBB,
+	[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] = 0xCC,
+	[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0xDD,
+	[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] = 0xEE,
+};
+
+static const s32 params_pen_some[] = {
+	[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xAA,
+	[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0xBB,
+};
+
+static const __u8 template_empty[] = { };
+static const __u8 template_small[] = { 0x00 };
+static const __u8 template_no_ph[] = { 0xAA, 0xFE, 0xAA, 0xED, 0x1D };
+
+static const __u8 template_pen_ph_end[] = {
+	0xAA, 0xBB, UCLOGIC_RDESC_PEN_PH_HEAD
+};
+
+static const __u8 template_pen_all_params[] = {
+	UCLOGIC_RDESC_PEN_PH(X_LM),
+	0x47, UCLOGIC_RDESC_PEN_PH(X_PM),
+	0x27, UCLOGIC_RDESC_PEN_PH(Y_LM),
+	UCLOGIC_RDESC_PEN_PH(Y_PM),
+	0x00, UCLOGIC_RDESC_PEN_PH(PRESSURE_LM),
+};
+
+static const __u8 expected_pen_all_params[] = {
+	0xAA, 0x00, 0x00, 0x00,
+	0x47, 0xBB, 0x00, 0x00, 0x00,
+	0x27, 0xCC, 0x00, 0x00, 0x00,
+	0xDD, 0x00, 0x00, 0x00,
+	0x00, 0xEE, 0x00, 0x00, 0x00,
+};
+
+static const __u8 template_pen_some_params[] = {
+	0x01, 0x02,
+	UCLOGIC_RDESC_PEN_PH(X_LM),
+	0x03, UCLOGIC_RDESC_PEN_PH(X_PM),
+	0x04, 0x05,
+};
+
+static const __u8 expected_pen_some_params[] = {
+	0x01, 0x02,
+	0xAA, 0x00, 0x00, 0x00,
+	0x03, 0xBB, 0x00, 0x00, 0x00,
+	0x04, 0x05,
+};
+
+static const __u8 template_params_none[] = {
+	0x27, UCLOGIC_RDESC_PEN_PH(Y_LM),
+	UCLOGIC_RDESC_PEN_PH(Y_PM),
+	0x00, UCLOGIC_RDESC_PEN_PH(PRESSURE_LM),
+};
+
+static struct uclogic_template_case uclogic_template_cases[] = {
+	{
+		.name = "Empty template",
+		.template = template_empty,
+		.template_size = sizeof(template_empty),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_empty,
+	},
+	{
+		.name = "Template smaller than the placeholder",
+		.template = template_small,
+		.template_size = sizeof(template_small),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_small,
+	},
+	{
+		.name = "No placeholder",
+		.template = template_no_ph,
+		.template_size = sizeof(template_no_ph),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_no_ph,
+	},
+	{
+		.name = "Pen placeholder at the end, without ID",
+		.template = template_pen_ph_end,
+		.template_size = sizeof(template_pen_ph_end),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_pen_ph_end,
+	},
+	{
+		.name = "All params present in the pen template",
+		.template = template_pen_all_params,
+		.template_size = sizeof(template_pen_all_params),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = expected_pen_all_params,
+	},
+	{
+		.name = "Some params present in the pen template (complete param list)",
+		.template = template_pen_some_params,
+		.template_size = sizeof(template_pen_some_params),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = expected_pen_some_params,
+	},
+	{
+		.name = "Some params present in the pen template (incomplete param list)",
+		.template = template_pen_some_params,
+		.template_size = sizeof(template_pen_some_params),
+		.param_list = params_pen_some,
+		.param_num = ARRAY_SIZE(params_pen_some),
+		.expected = expected_pen_some_params,
+	},
+	{
+		.name = "No params present in the template",
+		.template = template_params_none,
+		.template_size = sizeof(template_params_none),
+		.param_list = params_pen_some,
+		.param_num = ARRAY_SIZE(params_pen_some),
+		.expected = template_params_none,
+	},
+};
+
+static void uclogic_template_case_desc(struct uclogic_template_case *t,
+				       char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(uclogic_template, uclogic_template_cases,
+		  uclogic_template_case_desc);
+
+static void uclogic_template_test(struct kunit *test)
+{
+	__u8 *res;
+	const struct uclogic_template_case *params = test->param_value;
+
+	res = uclogic_rdesc_template_apply(params->template,
+					   params->template_size,
+					   params->param_list,
+					   params->param_num);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, res);
+	KUNIT_EXPECT_EQ(test, 0,
+			memcmp(res, params->expected, params->template_size));
+	kfree(res);
+}
+
+static struct kunit_case hid_uclogic_rdesc_test_cases[] = {
+	KUNIT_CASE_PARAM(uclogic_template_test, uclogic_template_gen_params),
+	{}
+};
+
+static struct kunit_suite hid_uclogic_rdesc_test_suite = {
+	.name = "hid-uclogic-rdesc-test",
+	.test_cases = hid_uclogic_rdesc_test_cases,
+};
+
+kunit_test_suite(hid_uclogic_rdesc_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for the UC-Logic driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("José Expósito <jose.exposito89@gmail.com>");
-- 
2.25.1

[PATCH for-5.19/uclogic v2 3/4] HID: uclogic: Allow to generate frame templates

[José Expósito]

Add a new template placeholder to allow configuring the number of
buttons in the drawing tablet frame and update the KUnit tests to
cover the new case.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
---
 drivers/hid/hid-uclogic-rdesc-test.c | 36 ++++++++++++++++++++++++++++
 drivers/hid/hid-uclogic-rdesc.c      | 14 ++++++++---
 drivers/hid/hid-uclogic-rdesc.h      |  6 +++++
 3 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/hid-uclogic-rdesc-test.c b/drivers/hid/hid-uclogic-rdesc-test.c
index ded59e226230..ebebffef5f8a 100644
--- a/drivers/hid/hid-uclogic-rdesc-test.c
+++ b/drivers/hid/hid-uclogic-rdesc-test.c
@@ -31,6 +31,10 @@ static const s32 params_pen_some[] = {
 	[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0xBB,
 };
 
+static const s32 params_frame_all[UCLOGIC_RDESC_PH_ID_NUM] = {
+	[UCLOGIC_RDESC_FRAME_PH_ID_UM] = 0xFF,
+};
+
 static const __u8 template_empty[] = { };
 static const __u8 template_small[] = { 0x00 };
 static const __u8 template_no_ph[] = { 0xAA, 0xFE, 0xAA, 0xED, 0x1D };
@@ -39,6 +43,10 @@ static const __u8 template_pen_ph_end[] = {
 	0xAA, 0xBB, UCLOGIC_RDESC_PEN_PH_HEAD
 };
 
+static const __u8 template_btn_ph_end[] = {
+	0xAA, 0xBB, UCLOGIC_RDESC_FRAME_PH_BTN_HEAD
+};
+
 static const __u8 template_pen_all_params[] = {
 	UCLOGIC_RDESC_PEN_PH(X_LM),
 	0x47, UCLOGIC_RDESC_PEN_PH(X_PM),
@@ -55,6 +63,18 @@ static const __u8 expected_pen_all_params[] = {
 	0x00, 0xEE, 0x00, 0x00, 0x00,
 };
 
+static const __u8 template_frame_all_params[] = {
+	0x01, 0x02,
+	UCLOGIC_RDESC_FRAME_PH_BTN,
+	0x99,
+};
+
+static const __u8 expected_frame_all_params[] = {
+	0x01, 0x02,
+	0x2A, 0xFF, 0x00,
+	0x99,
+};
+
 static const __u8 template_pen_some_params[] = {
 	0x01, 0x02,
 	UCLOGIC_RDESC_PEN_PH(X_LM),
@@ -108,6 +128,14 @@ static struct uclogic_template_case uclogic_template_cases[] = {
 		.param_num = ARRAY_SIZE(params_pen_all),
 		.expected = template_pen_ph_end,
 	},
+	{
+		.name = "Frame button placeholder at the end, without ID",
+		.template = template_btn_ph_end,
+		.template_size = sizeof(template_btn_ph_end),
+		.param_list = params_frame_all,
+		.param_num = ARRAY_SIZE(params_frame_all),
+		.expected = template_btn_ph_end,
+	},
 	{
 		.name = "All params present in the pen template",
 		.template = template_pen_all_params,
@@ -116,6 +144,14 @@ static struct uclogic_template_case uclogic_template_cases[] = {
 		.param_num = ARRAY_SIZE(params_pen_all),
 		.expected = expected_pen_all_params,
 	},
+	{
+		.name = "All params present in the frame template",
+		.template = template_frame_all_params,
+		.template_size = sizeof(template_frame_all_params),
+		.param_list = params_frame_all,
+		.param_num = ARRAY_SIZE(params_frame_all),
+		.expected = expected_frame_all_params,
+	},
 	{
 		.name = "Some params present in the pen template (complete param list)",
 		.template = template_pen_some_params,
diff --git a/drivers/hid/hid-uclogic-rdesc.c b/drivers/hid/hid-uclogic-rdesc.c
index 7126fba80968..3fb84ac492b4 100644
--- a/drivers/hid/hid-uclogic-rdesc.c
+++ b/drivers/hid/hid-uclogic-rdesc.c
@@ -979,7 +979,7 @@ const size_t uclogic_rdesc_xppen_deco01_frame_size =
  * uclogic_rdesc_template_apply() - apply report descriptor parameters to a
  * report descriptor template, creating a report descriptor. Copies the
  * template over to the new report descriptor and replaces every occurrence of
- * UCLOGIC_RDESC_PEN_PH_HEAD, followed by an index byte, with the value from the
+ * the template placeholders, followed by an index byte, with the value from the
  * parameter list at that index.
  *
  * @template_ptr:	Pointer to the template buffer.
@@ -996,6 +996,7 @@ __u8 *uclogic_rdesc_template_apply(const __u8 *template_ptr,
 				   const s32 *param_list,
 				   size_t param_num)
 {
+	static const __u8 btn_head[] = {UCLOGIC_RDESC_FRAME_PH_BTN_HEAD};
 	static const __u8 pen_head[] = {UCLOGIC_RDESC_PEN_PH_HEAD};
 	__u8 *rdesc_ptr;
 	__u8 *p;
@@ -1005,12 +1006,19 @@ __u8 *uclogic_rdesc_template_apply(const __u8 *template_ptr,
 	if (rdesc_ptr == NULL)
 		return NULL;
 
-	for (p = rdesc_ptr; p + sizeof(pen_head) < rdesc_ptr + template_size;) {
-		if (memcmp(p, pen_head, sizeof(pen_head)) == 0 &&
+	for (p = rdesc_ptr; p + sizeof(btn_head) < rdesc_ptr + template_size;) {
+		if (p + sizeof(pen_head) < rdesc_ptr + template_size &&
+		    memcmp(p, pen_head, sizeof(pen_head)) == 0 &&
 		    p[sizeof(pen_head)] < param_num) {
 			v = param_list[p[sizeof(pen_head)]];
 			put_unaligned(cpu_to_le32(v), (s32 *)p);
 			p += sizeof(pen_head) + 1;
+		} else if (memcmp(p, btn_head, sizeof(btn_head)) == 0 &&
+			   p[sizeof(btn_head)] < param_num) {
+			v = param_list[p[sizeof(btn_head)]];
+			put_unaligned((__u8)0x2A, p); /* Usage Maximum */
+			put_unaligned_le16((__force u16)cpu_to_le16(v), p + 1);
+			p += sizeof(btn_head) + 1;
 		} else {
 			p++;
 		}
diff --git a/drivers/hid/hid-uclogic-rdesc.h b/drivers/hid/hid-uclogic-rdesc.h
index 9d37090c39d1..3d78299f082d 100644
--- a/drivers/hid/hid-uclogic-rdesc.h
+++ b/drivers/hid/hid-uclogic-rdesc.h
@@ -82,6 +82,7 @@ extern const size_t uclogic_rdesc_twha60_fixed1_size;
 
 /* Report descriptor template placeholder head */
 #define UCLOGIC_RDESC_PEN_PH_HEAD	0xFE, 0xED, 0x1D
+#define UCLOGIC_RDESC_FRAME_PH_BTN_HEAD	0xFE, 0xED
 
 /* Apply report descriptor parameters to a report descriptor template */
 extern __u8 *uclogic_rdesc_template_apply(const __u8 *template_ptr,
@@ -96,6 +97,7 @@ enum uclogic_rdesc_ph_id {
 	UCLOGIC_RDESC_PEN_PH_ID_Y_LM,
 	UCLOGIC_RDESC_PEN_PH_ID_Y_PM,
 	UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM,
+	UCLOGIC_RDESC_FRAME_PH_ID_UM,
 	UCLOGIC_RDESC_PH_ID_NUM
 };
 
@@ -103,6 +105,10 @@ enum uclogic_rdesc_ph_id {
 #define UCLOGIC_RDESC_PEN_PH(_ID) \
 	UCLOGIC_RDESC_PEN_PH_HEAD, UCLOGIC_RDESC_PEN_PH_ID_##_ID
 
+/* Report descriptor frame buttons template placeholder */
+#define UCLOGIC_RDESC_FRAME_PH_BTN \
+	UCLOGIC_RDESC_FRAME_PH_BTN_HEAD, UCLOGIC_RDESC_FRAME_PH_ID_UM
+
 /* Report ID for v1 pen reports */
 #define UCLOGIC_RDESC_V1_PEN_ID	0x07
 
-- 
2.25.1

[PATCH for-5.19/uclogic v2 4/4] HID: uclogic: Add support for XP-PEN Deco L

[José Expósito]

The XP-PEN Deco L (UGEE) needs to be initialized by sending a buffer of
magic data, discovered by sniffing the Windows driver traffic.

In order to differentiate UGEE tablets that need this kind of
initialization from the previous ones, name them v2 internally and
create an entry point for them.

After initialization, the template report descriptors can be discovered
by parsing a string descriptor, similar to the one exposed by HUION v1
devices.

Add all the required elements to support the device.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
---
 drivers/hid/hid-ids.h            |   1 +
 drivers/hid/hid-uclogic-core.c   |   2 +
 drivers/hid/hid-uclogic-params.c | 197 +++++++++++++++++++++++++++++++
 drivers/hid/hid-uclogic-rdesc.c  | 102 ++++++++++++++++
 drivers/hid/hid-uclogic-rdesc.h  |   8 ++
 5 files changed, 310 insertions(+)

diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index f8b3774a3a10..ea4e60de46db 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -1272,6 +1272,7 @@
 #define USB_DEVICE_ID_UGEE_XPPEN_TABLET_G540	0x0075
 #define USB_DEVICE_ID_UGEE_XPPEN_TABLET_G640	0x0094
 #define USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO01	0x0042
+#define USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO_L	0x0935
 #define USB_DEVICE_ID_UGEE_XPPEN_TABLET_STAR06	0x0078
 #define USB_DEVICE_ID_UGEE_TABLET_G5		0x0074
 #define USB_DEVICE_ID_UGEE_TABLET_EX07S		0x0071
diff --git a/drivers/hid/hid-uclogic-core.c b/drivers/hid/hid-uclogic-core.c
index c0fe66e50c58..47a17375c7fc 100644
--- a/drivers/hid/hid-uclogic-core.c
+++ b/drivers/hid/hid-uclogic-core.c
@@ -521,6 +521,8 @@ static const struct hid_device_id uclogic_devices[] = {
 				USB_DEVICE_ID_UGEE_XPPEN_TABLET_G640) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_UGEE,
 				USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO01) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_UGEE,
+				USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO_L) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_UGEE,
 				USB_DEVICE_ID_UGEE_XPPEN_TABLET_STAR06) },
 	{ }
diff --git a/drivers/hid/hid-uclogic-params.c b/drivers/hid/hid-uclogic-params.c
index b43142f98a8b..f24a4aca7920 100644
--- a/drivers/hid/hid-uclogic-params.c
+++ b/drivers/hid/hid-uclogic-params.c
@@ -1002,6 +1002,197 @@ static int uclogic_params_huion_init(struct uclogic_params *params,
 	return rc;
 }
 
+/**
+ * uclogic_probe_interface() - some tablets, like the Parblo A610 PLUS V2 or
+ * the XP-PEN Deco Mini 7, need to be initialized by sending them magic data.
+ *
+ * @hdev:	The HID device of the tablet interface to initialize and get
+ *		parameters from. Cannot be NULL.
+ * @magic_arr:	The magic data that should be sent to probe the interface.
+ *		Cannot be NULL.
+ * @magic_size:	Size of the magic data.
+ * @endpoint:	Endpoint where the magic data should be sent.
+ *
+ * Returns:
+ *	Zero, if successful. A negative errno code on error.
+ */
+static int uclogic_probe_interface(struct hid_device *hdev, u8 *magic_arr,
+				   int magic_size, int endpoint)
+{
+	struct usb_device *udev;
+	unsigned int pipe = 0;
+	int sent;
+	u8 *buf = NULL;
+	int rc = 0;
+
+	if (!hdev || !magic_arr) {
+		rc = -EINVAL;
+		goto cleanup;
+	}
+
+	buf = kmemdup(magic_arr, magic_size, GFP_KERNEL);
+	if (!buf) {
+		rc = -ENOMEM;
+		goto cleanup;
+	}
+
+	udev = hid_to_usb_dev(hdev);
+	pipe = usb_sndintpipe(udev, endpoint);
+
+	rc = usb_interrupt_msg(udev, pipe, buf, magic_size, &sent, 1000);
+	if (rc || sent != magic_size) {
+		hid_err(hdev, "Interface probing failed: %d\n", rc);
+		rc = -1;
+		goto cleanup;
+	}
+
+	rc = 0;
+cleanup:
+	kfree(buf);
+	return rc;
+}
+
+/**
+ * uclogic_params_ugee_v2_init() - initialize a UGEE graphics tablets by
+ * discovering their parameters.
+ *
+ * These tables, internally designed as v2 to differentiate them from older
+ * models, expect a payload of magic data in orther to be switched to the fully
+ * functional mode and expose their parameters in a similar way to the
+ * information present in uclogic_params_pen_init_v1() but with some
+ * differences.
+ *
+ * @params:	Parameters to fill in (to be cleaned with
+ *		uclogic_params_cleanup()). Not modified in case of error.
+ *		Cannot be NULL.
+ * @hdev:	The HID device of the tablet interface to initialize and get
+ *		parameters from. Cannot be NULL.
+ *
+ * Returns:
+ *	Zero, if successful. A negative errno code on error.
+ */
+static int uclogic_params_ugee_v2_init(struct uclogic_params *params,
+				       struct hid_device *hdev)
+{
+	int rc = 0;
+	struct usb_interface *iface;
+	__u8 bInterfaceNumber;
+	const int str_desc_len = 12;
+	__u8 *str_desc = NULL;
+	__u8 *rdesc_pen = NULL;
+	__u8 *rdesc_frame = NULL;
+	s32 desc_params[UCLOGIC_RDESC_PH_ID_NUM];
+	s32 resolution;
+	__u8 magic_arr[] = {
+		0x02, 0xb0, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+	};
+	/* The resulting parameters (noop) */
+	struct uclogic_params p = {0, };
+
+	if (!params || !hdev) {
+		rc = -EINVAL;
+		goto cleanup;
+	}
+
+	iface = to_usb_interface(hdev->dev.parent);
+	bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
+	if (bInterfaceNumber != 2) {
+		uclogic_params_init_invalid(&p);
+		goto output;
+	}
+
+	/*
+	 * Initialize the interface by sending magic data.
+	 * The specific data was discovered by sniffing the Windows driver
+	 * traffic.
+	 */
+	rc = uclogic_probe_interface(hdev, magic_arr, sizeof(magic_arr), 0x03);
+	if (rc) {
+		uclogic_params_init_invalid(&p);
+		goto output;
+	}
+
+	/*
+	 * Read the string descriptor containing pen and frame parameters.
+	 * The specific string descriptor and data were discovered by sniffing
+	 * the Windows driver traffic.
+	 */
+	rc = uclogic_params_get_str_desc(&str_desc, hdev, 100, str_desc_len);
+	if (rc != str_desc_len) {
+		hid_err(hdev, "failed retrieving pen and frame parameters: %d\n", rc);
+		uclogic_params_init_invalid(&p);
+		goto output;
+	}
+
+	desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] =
+		get_unaligned_le16(str_desc + 2);
+	desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] =
+		get_unaligned_le16(str_desc + 4);
+	desc_params[UCLOGIC_RDESC_FRAME_PH_ID_UM] = str_desc[6];
+	desc_params[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] =
+		get_unaligned_le16(str_desc + 8);
+	resolution = get_unaligned_le16(str_desc + 10);
+	if (resolution == 0) {
+		desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0;
+		desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0;
+	} else {
+		desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] =
+			desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] * 1000 /
+			resolution;
+		desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] =
+			desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] * 1000 /
+			resolution;
+	}
+	kfree(str_desc);
+	str_desc = NULL;
+
+	/* Initialize the pen interface */
+	rdesc_pen = uclogic_rdesc_template_apply(
+				uclogic_rdesc_ugee_v2_pen_template_arr,
+				uclogic_rdesc_ugee_v2_pen_template_size,
+				desc_params, ARRAY_SIZE(desc_params));
+	if (!rdesc_pen) {
+		rc = -ENOMEM;
+		goto cleanup;
+	}
+
+	p.pen.desc_ptr = rdesc_pen;
+	p.pen.desc_size = uclogic_rdesc_ugee_v2_pen_template_size;
+	p.pen.id = 0x02;
+	p.pen.subreport_list[0].value = 0xf0;
+	p.pen.subreport_list[0].id = UCLOGIC_RDESC_V1_FRAME_ID;
+
+	/* Initialize the frame interface */
+	rdesc_frame = uclogic_rdesc_template_apply(
+				uclogic_rdesc_ugee_v2_frame_btn_template_arr,
+				uclogic_rdesc_ugee_v2_frame_btn_template_size,
+				desc_params, ARRAY_SIZE(desc_params));
+	if (!rdesc_frame) {
+		rc = -ENOMEM;
+		goto cleanup;
+	}
+
+	rc = uclogic_params_frame_init_with_desc(&p.frame_list[0],
+						 rdesc_frame,
+						 uclogic_rdesc_ugee_v2_frame_btn_template_size,
+						 UCLOGIC_RDESC_V1_FRAME_ID);
+	kfree(rdesc_frame);
+	if (rc) {
+		uclogic_params_init_invalid(&p);
+		goto output;
+	}
+
+output:
+	/* Output parameters */
+	memcpy(params, &p, sizeof(*params));
+	memset(&p, 0, sizeof(p));
+	rc = 0;
+cleanup:
+	kfree(str_desc);
+	uclogic_params_cleanup(&p);
+	return rc;
+}
+
 /**
  * uclogic_params_init() - initialize a tablet interface and discover its
  * parameters.
@@ -1237,6 +1428,12 @@ int uclogic_params_init(struct uclogic_params *params,
 			uclogic_params_init_invalid(&p);
 		}
 		break;
+	case VID_PID(USB_VENDOR_ID_UGEE,
+		     USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO_L):
+		rc = uclogic_params_ugee_v2_init(&p, hdev);
+		if (rc != 0)
+			goto cleanup;
+		break;
 	case VID_PID(USB_VENDOR_ID_TRUST,
 		     USB_DEVICE_ID_TRUST_PANORA_TABLET):
 	case VID_PID(USB_VENDOR_ID_UGEE,
diff --git a/drivers/hid/hid-uclogic-rdesc.c b/drivers/hid/hid-uclogic-rdesc.c
index 3fb84ac492b4..3d68e8b0784d 100644
--- a/drivers/hid/hid-uclogic-rdesc.c
+++ b/drivers/hid/hid-uclogic-rdesc.c
@@ -859,6 +859,108 @@ const __u8 uclogic_rdesc_v2_frame_dial_arr[] = {
 const size_t uclogic_rdesc_v2_frame_dial_size =
 			sizeof(uclogic_rdesc_v2_frame_dial_arr);
 
+/* Fixed report descriptor template for UGEE v2 pen reports */
+const __u8 uclogic_rdesc_ugee_v2_pen_template_arr[] = {
+	0x05, 0x0d,         /*  Usage Page (Digitizers),                */
+	0x09, 0x01,         /*  Usage (Digitizer),                      */
+	0xa1, 0x01,         /*  Collection (Application),               */
+	0x85, 0x02,         /*      Report ID (2),                      */
+	0x09, 0x20,         /*      Usage (Stylus),                     */
+	0xa1, 0x00,         /*      Collection (Physical),              */
+	0x09, 0x42,         /*          Usage (Tip Switch),             */
+	0x09, 0x44,         /*          Usage (Barrel Switch),          */
+	0x09, 0x46,         /*          Usage (Tablet Pick),            */
+	0x75, 0x01,         /*          Report Size (1),                */
+	0x95, 0x03,         /*          Report Count (3),               */
+	0x14,               /*          Logical Minimum (0),            */
+	0x25, 0x01,         /*          Logical Maximum (1),            */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0x95, 0x02,         /*          Report Count (2),               */
+	0x81, 0x03,         /*          Input (Constant, Variable),     */
+	0x09, 0x32,         /*          Usage (In Range),               */
+	0x95, 0x01,         /*          Report Count (1),               */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0x95, 0x02,         /*          Report Count (2),               */
+	0x81, 0x03,         /*          Input (Constant, Variable),     */
+	0x75, 0x10,         /*          Report Size (16),               */
+	0x95, 0x01,         /*          Report Count (1),               */
+	0x35, 0x00,         /*          Physical Minimum (0),           */
+	0xa4,               /*          Push,                           */
+	0x05, 0x01,         /*          Usage Page (Desktop),           */
+	0x09, 0x30,         /*          Usage (X),                      */
+	0x65, 0x13,         /*          Unit (Inch),                    */
+	0x55, 0x0d,         /*          Unit Exponent (-3),             */
+	0x27, UCLOGIC_RDESC_PEN_PH(X_LM),
+			    /*          Logical Maximum (PLACEHOLDER),  */
+	0x47, UCLOGIC_RDESC_PEN_PH(X_PM),
+			    /*          Physical Maximum (PLACEHOLDER), */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0x09, 0x31,         /*          Usage (Y),                      */
+	0x27, UCLOGIC_RDESC_PEN_PH(Y_LM),
+			    /*          Logical Maximum (PLACEHOLDER),  */
+	0x47, UCLOGIC_RDESC_PEN_PH(Y_PM),
+			    /*          Physical Maximum (PLACEHOLDER), */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0xb4,               /*          Pop,                            */
+	0x09, 0x30,         /*          Usage (Tip Pressure),           */
+	0x45, 0x00,         /*          Physical Maximum (0),           */
+	0x27, UCLOGIC_RDESC_PEN_PH(PRESSURE_LM),
+			    /*          Logical Maximum (PLACEHOLDER),  */
+	0x75, 0x0D,         /*          Report Size (13),               */
+	0x95, 0x01,         /*          Report Count (1),               */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0x75, 0x01,         /*          Report Size (1),                */
+	0x95, 0x03,         /*          Report Count (3),               */
+	0x81, 0x01,         /*          Input (Constant),               */
+	0x09, 0x3d,         /*          Usage (X Tilt),                 */
+	0x35, 0xC3,         /*          Physical Minimum (-61),         */
+	0x45, 0x3C,         /*          Physical Maximum (60),          */
+	0x15, 0xC3,         /*          Logical Minimum (-61),          */
+	0x25, 0x3C,         /*          Logical Maximum (60),           */
+	0x75, 0x08,         /*          Report Size (8),                */
+	0x95, 0x01,         /*          Report Count (1),               */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0x09, 0x3e,         /*          Usage (Y Tilt),                 */
+	0x35, 0xC3,         /*          Physical Minimum (-61),         */
+	0x45, 0x3C,         /*          Physical Maximum (60),          */
+	0x15, 0xC3,         /*          Logical Minimum (-61),          */
+	0x25, 0x3C,         /*          Logical Maximum (60),           */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0xc0,               /*      End Collection,                     */
+	0xc0,               /*  End Collection                          */
+};
+const size_t uclogic_rdesc_ugee_v2_pen_template_size =
+			sizeof(uclogic_rdesc_ugee_v2_pen_template_arr);
+
+/* Fixed report descriptor template for UGEE v2 frame reports (buttons only) */
+const __u8 uclogic_rdesc_ugee_v2_frame_btn_template_arr[] = {
+	0x05, 0x01,         /*  Usage Page (Desktop),                   */
+	0x09, 0x07,         /*  Usage (Keypad),                         */
+	0xA1, 0x01,         /*  Collection (Application),               */
+	0x85, UCLOGIC_RDESC_V1_FRAME_ID,
+			    /*      Report ID,                          */
+	0x05, 0x0D,         /*      Usage Page (Digitizer),             */
+	0x09, 0x39,         /*      Usage (Tablet Function Keys),       */
+	0xA0,               /*      Collection (Physical),              */
+	0x75, 0x01,         /*          Report Size (1),                */
+	0x95, 0x08,         /*          Report Count (8),               */
+	0x81, 0x01,         /*          Input (Constant),               */
+	0x05, 0x09,         /*          Usage Page (Button),            */
+	0x19, 0x01,         /*          Usage Minimum (01h),            */
+	UCLOGIC_RDESC_FRAME_PH_BTN,
+			    /*          Usage Maximum (PLACEHOLDER),    */
+	0x95, 0x0A,         /*          Report Count (10),              */
+	0x14,               /*          Logical Minimum (0),            */
+	0x25, 0x01,         /*          Logical Maximum (1),            */
+	0x81, 0x02,         /*          Input (Variable),               */
+	0x95, 0x46,         /*          Report Count (70),              */
+	0x81, 0x01,         /*          Input (Constant),               */
+	0xC0,               /*      End Collection,                     */
+	0xC0                /*  End Collection                          */
+};
+const size_t uclogic_rdesc_ugee_v2_frame_btn_template_size =
+			sizeof(uclogic_rdesc_ugee_v2_frame_btn_template_arr);
+
 /* Fixed report descriptor for Ugee EX07 frame */
 const __u8 uclogic_rdesc_ugee_ex07_frame_arr[] = {
 	0x05, 0x01,             /*  Usage Page (Desktop),                   */
diff --git a/drivers/hid/hid-uclogic-rdesc.h b/drivers/hid/hid-uclogic-rdesc.h
index 3d78299f082d..86e64a9ee6bd 100644
--- a/drivers/hid/hid-uclogic-rdesc.h
+++ b/drivers/hid/hid-uclogic-rdesc.h
@@ -161,6 +161,14 @@ extern const size_t uclogic_rdesc_v2_frame_dial_size;
 /* Device ID byte offset in v2 frame dial reports */
 #define UCLOGIC_RDESC_V2_FRAME_DIAL_DEV_ID_BYTE	0x4
 
+/* Fixed report descriptor template for UGEE v2 pen reports */
+extern const __u8 uclogic_rdesc_ugee_v2_pen_template_arr[];
+extern const size_t uclogic_rdesc_ugee_v2_pen_template_size;
+
+/* Fixed report descriptor template for UGEE v2 frame reports (buttons only) */
+extern const __u8 uclogic_rdesc_ugee_v2_frame_btn_template_arr[];
+extern const size_t uclogic_rdesc_ugee_v2_frame_btn_template_size;
+
 /* Fixed report descriptor for Ugee EX07 frame */
 extern const __u8 uclogic_rdesc_ugee_ex07_frame_arr[];
 extern const size_t uclogic_rdesc_ugee_ex07_frame_size;
-- 
2.25.1

[PATCH for-5.19/uclogic] HID: uclogic: Remove useless loop

[Stefan Berzl]

The while in question does nothing except provide the possibility
to have an infinite loop in case the subreport id is actually the same
as the pen id.

Signed-off-by: Stefan Berzl <stefanberzl@gmail.com>

---
 drivers/hid/hid-uclogic-core.c | 55 ++++++++++++++++------------------
 1 file changed, 25 insertions(+), 30 deletions(-)

diff --git a/drivers/hid/hid-uclogic-core.c b/drivers/hid/hid-uclogic-core.c
index c0fe66e50c58..1a6b941f3964 100644
--- a/drivers/hid/hid-uclogic-core.c
+++ b/drivers/hid/hid-uclogic-core.c
@@ -423,40 +423,35 @@ static int uclogic_raw_event(struct hid_device *hdev,
 	if (report->type != HID_INPUT_REPORT)
 		return 0;
 
-	while (true) {
-		/* Tweak pen reports, if necessary */
-		if ((report_id == params->pen.id) && (size >= 2)) {
-			subreport_list_end =
-				params->pen.subreport_list +
-				ARRAY_SIZE(params->pen.subreport_list);
-			/* Try to match a subreport */
-			for (subreport = params->pen.subreport_list;
-			     subreport < subreport_list_end; subreport++) {
-				if (subreport->value != 0 &&
-				    subreport->value == data[1]) {
-					break;
-				}
-			}
-			/* If a subreport matched */
-			if (subreport < subreport_list_end) {
-				/* Change to subreport ID, and restart */
-				report_id = data[0] = subreport->id;
-				continue;
-			} else {
-				return uclogic_raw_event_pen(drvdata, data, size);
+	/* Tweak pen reports, if necessary */
+	if ((report_id == params->pen.id) && (size >= 2)) {
+		subreport_list_end =
+			params->pen.subreport_list +
+			ARRAY_SIZE(params->pen.subreport_list);
+		/* Try to match a subreport */
+		for (subreport = params->pen.subreport_list;
+		     subreport < subreport_list_end; subreport++) {
+			if (subreport->value != 0 &&
+			    subreport->value == data[1]) {
+				break;
 			}
 		}
-
-		/* Tweak frame control reports, if necessary */
-		for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
-			if (report_id == params->frame_list[i].id) {
-				return uclogic_raw_event_frame(
-					drvdata, &params->frame_list[i],
-					data, size);
-			}
+		/* If a subreport matched */
+		if (subreport < subreport_list_end) {
+			/* Change to subreport ID, and restart */
+			report_id = data[0] = subreport->id;
+		} else {
+			return uclogic_raw_event_pen(drvdata, data, size);
 		}
+	}
 
-		break;
+	/* Tweak frame control reports, if necessary */
+	for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
+		if (report_id == params->frame_list[i].id) {
+			return uclogic_raw_event_frame(
+				drvdata, &params->frame_list[i],
+				data, size);
+		}
 	}
 
 	return 0;
-- 
2.36.1

Re: [PATCH for-5.19/uclogic] HID: uclogic: Remove useless loop

[José Expósito]

Hi Stefan,

Thanks for the patch. You can send it as an standalone patch rather
than as a response to my patches, I don't know if it could be missed by
maintaners this way.

On Sun, May 29, 2022 at 11:49:46PM +0200, Stefan Berzl wrote:
> The while in question does nothing except provide the possibility
> to have an infinite loop in case the subreport id is actually the same
> as the pen id.
> 
> Signed-off-by: Stefan Berzl <stefanberzl@gmail.com>
> 
> ---
>  drivers/hid/hid-uclogic-core.c | 55 ++++++++++++++++------------------
>  1 file changed, 25 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/hid/hid-uclogic-core.c b/drivers/hid/hid-uclogic-core.c
> index c0fe66e50c58..1a6b941f3964 100644
> --- a/drivers/hid/hid-uclogic-core.c
> +++ b/drivers/hid/hid-uclogic-core.c
> @@ -423,40 +423,35 @@ static int uclogic_raw_event(struct hid_device *hdev,
>  	if (report->type != HID_INPUT_REPORT)
>  		return 0;
>  
> -	while (true) {
> -		/* Tweak pen reports, if necessary */
> -		if ((report_id == params->pen.id) && (size >= 2)) {
> -			subreport_list_end =
> -				params->pen.subreport_list +
> -				ARRAY_SIZE(params->pen.subreport_list);
> -			/* Try to match a subreport */
> -			for (subreport = params->pen.subreport_list;
> -			     subreport < subreport_list_end; subreport++) {
> -				if (subreport->value != 0 &&
> -				    subreport->value == data[1]) {
> -					break;
> -				}
> -			}
> -			/* If a subreport matched */
> -			if (subreport < subreport_list_end) {
> -				/* Change to subreport ID, and restart */
> -				report_id = data[0] = subreport->id;
> -				continue;

Here, in the previous code, the "report_id" is set to the subreport ID
and the while loop is executed again with the new ID. The loop acts as
a recursive function.

Isn't this behaviour removed by your patch?

Jose

> -			} else {
> -				return uclogic_raw_event_pen(drvdata, data, size);
> +	/* Tweak pen reports, if necessary */
> +	if ((report_id == params->pen.id) && (size >= 2)) {
> +		subreport_list_end =
> +			params->pen.subreport_list +
> +			ARRAY_SIZE(params->pen.subreport_list);
> +		/* Try to match a subreport */
> +		for (subreport = params->pen.subreport_list;
> +		     subreport < subreport_list_end; subreport++) {
> +			if (subreport->value != 0 &&
> +			    subreport->value == data[1]) {
> +				break;
>  			}
>  		}
> -
> -		/* Tweak frame control reports, if necessary */
> -		for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
> -			if (report_id == params->frame_list[i].id) {
> -				return uclogic_raw_event_frame(
> -					drvdata, &params->frame_list[i],
> -					data, size);
> -			}
> +		/* If a subreport matched */
> +		if (subreport < subreport_list_end) {
> +			/* Change to subreport ID, and restart */
> +			report_id = data[0] = subreport->id;
> +		} else {
> +			return uclogic_raw_event_pen(drvdata, data, size);
>  		}
> +	}
>  
> -		break;
> +	/* Tweak frame control reports, if necessary */
> +	for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
> +		if (report_id == params->frame_list[i].id) {
> +			return uclogic_raw_event_frame(
> +				drvdata, &params->frame_list[i],
> +				data, size);
> +		}
>  	}
>  
>  	return 0;
> -- 
> 2.36.1
> 
> 

Re: [PATCH for-5.19/uclogic] HID: uclogic: Remove useless loop

[Stefan Berzl]

Hello everynyan!

> Hi Stefan,
> 
> Thanks for the patch. You can send it as an standalone patch rather
> than as a response to my patches, I don't know if it could be missed by
> maintaners this way.

You are right about that, I'll keep it in mind. But for consistency,
I think it's better to reply here for now.

>> The while in question does nothing except provide the possibility
>> to have an infinite loop in case the subreport id is actually the same
>> as the pen id.
>>
>> Signed-off-by: Stefan Berzl <stefanberzl@gmail.com>
>>
>> ---
>>  drivers/hid/hid-uclogic-core.c | 55 ++++++++++++++++------------------
>>  1 file changed, 25 insertions(+), 30 deletions(-)
>>
>> diff --git a/drivers/hid/hid-uclogic-core.c b/drivers/hid/hid-uclogic-core.c
>> index c0fe66e50c58..1a6b941f3964 100644
>> --- a/drivers/hid/hid-uclogic-core.c
>> +++ b/drivers/hid/hid-uclogic-core.c
>> @@ -423,40 +423,35 @@ static int uclogic_raw_event(struct hid_device *hdev,
>>  	if (report->type != HID_INPUT_REPORT)
>>  		return 0;
>>  
>> -	while (true) {
>> -		/* Tweak pen reports, if necessary */
>> -		if ((report_id == params->pen.id) && (size >= 2)) {
>> -			subreport_list_end =
>> -				params->pen.subreport_list +
>> -				ARRAY_SIZE(params->pen.subreport_list);
>> -			/* Try to match a subreport */
>> -			for (subreport = params->pen.subreport_list;
>> -			     subreport < subreport_list_end; subreport++) {
>> -				if (subreport->value != 0 &&
>> -				    subreport->value == data[1]) {
>> -					break;
>> -				}
>> -			}
>> -			/* If a subreport matched */
>> -			if (subreport < subreport_list_end) {
>> -				/* Change to subreport ID, and restart */
>> -				report_id = data[0] = subreport->id;
>> -				continue;
> 
> Here, in the previous code, the "report_id" is set to the subreport ID
> and the while loop is executed again with the new ID. The loop acts as
> a recursive function.
> 
> Isn't this behaviour removed by your patch?
> 
> Jose

Think about what this behavior really achieves. In the first iteration,
we check if params->pen.id equals the report_id, which is the actual
report id from the usb message. If that is the case, we check if the
second byte of the message is such that we need an updated "subreport"
for this particular message. Therefore, the report_id is set to the
subreport->id. This subreport->id is by design supposed to be different
from the original params->pen.id, because otherwise, why would we need  
this update? If we then "continue" with this useless loop, either one of
two cases can happen:

The best case is that the (report_id = subreport->id) != params->pen.id 
in which case the if-block won't be executed and we only wasted time.

If the (report_id = subreport->id) == params->pen.id however, things get
interesting. The "subreport_list_end" and "subreport" variables will
again be set to entries based on "params->pen.subreport_list", which is
totally unchanged from the last iteration. We will iterate the same
subreports, find the same result, set report_id to the same
subreport->id and, that's the beauty of it, "continue" this ingenious
loop, creating an infinite loop.

This contraption is in the best case only wasteful, yet it has been
accepted all willy-nilly like. Really gets the noggin joggin.

> 
>> -			} else {
>> -				return uclogic_raw_event_pen(drvdata, data, size);
>> +	/* Tweak pen reports, if necessary */
>> +	if ((report_id == params->pen.id) && (size >= 2)) {
>> +		subreport_list_end =
>> +			params->pen.subreport_list +
>> +			ARRAY_SIZE(params->pen.subreport_list);
>> +		/* Try to match a subreport */
>> +		for (subreport = params->pen.subreport_list;
>> +		     subreport < subreport_list_end; subreport++) {
>> +			if (subreport->value != 0 &&
>> +			    subreport->value == data[1]) {
>> +				break;
>>  			}
>>  		}
>> -
>> -		/* Tweak frame control reports, if necessary */
>> -		for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
>> -			if (report_id == params->frame_list[i].id) {
>> -				return uclogic_raw_event_frame(
>> -					drvdata, &params->frame_list[i],
>> -					data, size);
>> -			}
>> +		/* If a subreport matched */
>> +		if (subreport < subreport_list_end) {
>> +			/* Change to subreport ID, and restart */
>> +			report_id = data[0] = subreport->id;
>> +		} else {
>> +			return uclogic_raw_event_pen(drvdata, data, size);
>>  		}
>> +	}
>>  
>> -		break;
>> +	/* Tweak frame control reports, if necessary */
>> +	for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
>> +		if (report_id == params->frame_list[i].id) {
>> +			return uclogic_raw_event_frame(
>> +				drvdata, &params->frame_list[i],
>> +				data, size);
>> +		}
>>  	}
>>  
>>  	return 0;
>> -- 
>> 2.36.1
>>
>>

Bye bye

Stefan Berzl

Re: [PATCH for-5.19/uclogic] HID: uclogic: Remove useless loop

[José Expósito]

On Mon, May 30, 2022 at 06:46:38PM +0200, Stefan Berzl wrote:
> Think about what this behavior really achieves. In the first iteration,
> we check if params->pen.id equals the report_id, which is the actual
> report id from the usb message. If that is the case, we check if the
> second byte of the message is such that we need an updated "subreport"
> for this particular message. Therefore, the report_id is set to the
> subreport->id. This subreport->id is by design supposed to be different
> from the original params->pen.id, because otherwise, why would we need  
> this update? If we then "continue" with this useless loop, either one of
> two cases can happen:
> 
> The best case is that the (report_id = subreport->id) != params->pen.id 
> in which case the if-block won't be executed and we only wasted time.
> 
> If the (report_id = subreport->id) == params->pen.id however, things get
> interesting. The "subreport_list_end" and "subreport" variables will
> again be set to entries based on "params->pen.subreport_list", which is
> totally unchanged from the last iteration. We will iterate the same
> subreports, find the same result, set report_id to the same
> subreport->id and, that's the beauty of it, "continue" this ingenious
> loop, creating an infinite loop.

True, data[1] doesn't change, so an extra if is executed for no reason.
I mean, it is not dramatic, but I guess the while loop could be removed
for clarity.

I wonder why it was implemented in a loop though, check commit
8b013098be ("HID: uclogic: Replace pen_frame_flag with subreport_list").

The while loop is intrudeced there and I can imagine that for a good
reason... However, I can not think in a case where removing the loop
could cause issues.

> This contraption is in the best case only wasteful, yet it has been
> accepted all willy-nilly like. Really gets the noggin joggin.
> 
> > 
> >> -			} else {
> >> -				return uclogic_raw_event_pen(drvdata, data, size);
> >> +	/* Tweak pen reports, if necessary */
> >> +	if ((report_id == params->pen.id) && (size >= 2)) {
> >> +		subreport_list_end =
> >> +			params->pen.subreport_list +
> >> +			ARRAY_SIZE(params->pen.subreport_list);
> >> +		/* Try to match a subreport */
> >> +		for (subreport = params->pen.subreport_list;
> >> +		     subreport < subreport_list_end; subreport++) {
> >> +			if (subreport->value != 0 &&
> >> +			    subreport->value == data[1]) {
> >> +				break;
> >>  			}
> >>  		}
> >> -
> >> -		/* Tweak frame control reports, if necessary */
> >> -		for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
> >> -			if (report_id == params->frame_list[i].id) {
> >> -				return uclogic_raw_event_frame(
> >> -					drvdata, &params->frame_list[i],
> >> -					data, size);
> >> -			}
> >> +		/* If a subreport matched */
> >> +		if (subreport < subreport_list_end) {
> >> +			/* Change to subreport ID, and restart */
> >> +			report_id = data[0] = subreport->id;
> >> +		} else {
> >> +			return uclogic_raw_event_pen(drvdata, data, size);
> >>  		}
> >> +	}
> >>  
> >> -		break;
> >> +	/* Tweak frame control reports, if necessary */
> >> +	for (i = 0; i < ARRAY_SIZE(params->frame_list); i++) {
> >> +		if (report_id == params->frame_list[i].id) {
> >> +			return uclogic_raw_event_frame(
> >> +				drvdata, &params->frame_list[i],
> >> +				data, size);
> >> +		}
> >>  	}
> >>  
> >>  	return 0;
> >> -- 
> >> 2.36.1
> >>
> >>
> 
> Bye bye
> 
> Stefan Berzl