[igt-dev] [PATCH i-g-t] lib/i915: Add a helper lib to read mmio registers via ioctl

[Alan Previn]

Add a helper lib function to call DRM_IOCTL_I915_REG_READ to
read whitelisted registers.

Signed-off-by: Alan Previn <alan.previn.teres.alexis at intel.com>
---
 lib/i915/i915_reg_read_ioctl.c | 34 ++++++++++++++++++++++++++++++++++
 lib/i915/i915_reg_read_ioctl.h |  9 +++++++++
 lib/meson.build                |  1 +
 tests/i915/gem_reg_read.c      | 26 ++++++--------------------
 tests/i915/i915_pm_rpm.c       |  9 +++++----
 5 files changed, 55 insertions(+), 24 deletions(-)
 create mode 100644 lib/i915/i915_reg_read_ioctl.c
 create mode 100644 lib/i915/i915_reg_read_ioctl.h

diff --git a/lib/i915/i915_reg_read_ioctl.c b/lib/i915/i915_reg_read_ioctl.c
new file mode 100644
index 000000000..a0fa654e5
--- /dev/null
+++ b/lib/i915/i915_reg_read_ioctl.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2023 Intel Corporation
+ */
+
+#include "i915/i915_reg_read_ioctl.h"
+#include "igt_device.h"
+
+/**
+ * i915_reg_read_ioctl:
+ * @drmfd: device file descriptor
+ * @offset: mmio register to read from
+ * @value: ptr to fill with results from read
+ *
+ * This function uses DRM_IOCTL_I915_REG_READ to read the
+ * register and so it can return NOACCES if i915 doesn't allow.
+ *
+ * Returns:
+ * -errno
+ */
+int i915_reg_read_ioctl(int drmfd, __u64 offset, __u64 *value)
+{
+	struct drm_i915_reg_read reg_read = {0};
+	int ret = 0;
+
+	reg_read.offset = offset;
+	if (igt_ioctl(drmfd, DRM_IOCTL_I915_REG_READ, &reg_read))
+		ret = -errno;
+	else if (value)
+		*value = reg_read.val;
+
+	return ret;
+}
+
diff --git a/lib/i915/i915_reg_read_ioctl.h b/lib/i915/i915_reg_read_ioctl.h
new file mode 100644
index 000000000..cb1bb3950
--- /dev/null
+++ b/lib/i915/i915_reg_read_ioctl.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright(c) 2023 Intel Corporation. All rights reserved.
+ */
+
+#include "igt.h"
+
+int i915_reg_read_ioctl(int drmfd, __u64 offset, __u64 *value);
+
diff --git a/lib/meson.build b/lib/meson.build
index ce11c0715..6303930d9 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -14,6 +14,7 @@ lib_sources = [
 	'i915/intel_decode.c',
 	'i915/intel_memory_region.c',
 	'i915/i915_crc.c',
+	'i915/i915_reg_read_ioctl.c',
 	'igt_collection.c',
 	'igt_color_encoding.c',
 	'igt_crc.c',
diff --git a/tests/i915/gem_reg_read.c b/tests/i915/gem_reg_read.c
index de6788abe..1af7c517f 100644
--- a/tests/i915/gem_reg_read.c
+++ b/tests/i915/gem_reg_read.c
@@ -32,6 +32,8 @@
 #include <sys/utsname.h>
 #include <time.h>
 
+#include "i915/i915_reg_read_ioctl.h"
+
 /**
  * TEST: gem reg read
  * Feature: gem_core
@@ -52,24 +54,8 @@ struct local_drm_i915_reg_read {
 	__u64 val; /* Return value */
 };
 
-#define REG_READ_IOCTL DRM_IOWR(DRM_COMMAND_BASE + 0x31, struct local_drm_i915_reg_read)
-
 #define RENDER_RING_TIMESTAMP 0x2358
 
-static int read_register(int fd, uint64_t offset, uint64_t * val)
-{
-	int ret = 0;
-	struct local_drm_i915_reg_read reg_read;
-	reg_read.offset = offset;
-
-	if (drmIoctl(fd, REG_READ_IOCTL, &reg_read))
-		ret = -errno;
-
-	*val = reg_read.val;
-
-	return ret;
-}
-
 static bool check_kernel_x86_64(void)
 {
 	int ret;
@@ -87,9 +73,9 @@ static bool check_kernel_x86_64(void)
 static bool check_timestamp(int fd)
 {
 	int ret;
-	uint64_t val;
+	__u64 val;
 
-	ret = read_register(fd, RENDER_RING_TIMESTAMP | 1, &val);
+	ret = i915_reg_read_ioctl(fd, RENDER_RING_TIMESTAMP | 1, &val);
 
 	return ret == 0;
 }
@@ -103,7 +89,7 @@ static int timer_query(int fd, uint64_t * val)
 	if (has_proper_timestamp)
 		offset |= 1;
 
-	ret = read_register(fd, offset, val);
+	ret = i915_reg_read_ioctl(fd, offset, (__u64 *)val);
 
 /*
  * When reading the timestamp register with single 64b read, we are observing
@@ -168,7 +154,7 @@ igt_main
 	}
 
 	igt_subtest("bad-register")
-		igt_assert_eq(read_register(fd, 0x12345678, &val), -EINVAL);
+		igt_assert_eq(i915_reg_read_ioctl(fd, 0x12345678, (__u64 *)&val), -EINVAL);
 
 	igt_subtest("timestamp-moving") {
 		igt_skip_on(timer_query(fd, &val) != 0);
diff --git a/tests/i915/i915_pm_rpm.c b/tests/i915/i915_pm_rpm.c
index 17413ffe5..b19accdc9 100644
--- a/tests/i915/i915_pm_rpm.c
+++ b/tests/i915/i915_pm_rpm.c
@@ -40,6 +40,9 @@
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+
+#include "i915/i915_reg_read_ioctl.h"
+
 /**
  * TEST: i915 pm rpm
  *
@@ -1852,13 +1855,11 @@ static void gem_evict_pwrite_subtest(void)
 /* This also triggered WARNs on dmesg at some point. */
 static void reg_read_ioctl_subtest(void)
 {
-	struct drm_i915_reg_read rr = {
-		.offset = 0x2358, /* render ring timestamp */
-	};
+	__u64 val;
 
 	disable_all_screens_and_wait(&ms_data);
 
-	do_ioctl(drm_fd, DRM_IOCTL_I915_REG_READ, &rr);
+	i915_reg_read_ioctl(drm_fd, 0x2358, &val);
 
 	igt_assert(wait_for_suspended());
 }

base-commit: 81e08c6d648e949df161a4f39118ed3eb1e354e9
-- 
2.39.0