[PATCH 348/379][SRU][OEM-5.6] bus: mhi: core: Introduce sysfs entries for MHI

[You-Sheng Yang]

From: Bhaumik Bhatt <bbhatt at codeaurora.org>

BugLink: https://bugs.launchpad.net/bugs/1879633

Introduce sysfs entries to enable userspace clients the ability to read
the serial number and the OEM PK Hash values obtained from BHI. OEMs
need to read these device-specific hardware information values through
userspace for factory testing purposes and cannot be exposed via degbufs
as it may remain disabled for performance reasons. Also, update the
documentation for ABI to include these entries.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org>
[mani: used dev_groups to manage sysfs attributes]
Signed-off-by: Bhaumik Bhatt <bbhatt at codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org>
Link: https://lore.kernel.org/r/20200929175218.8178-16-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit 21cb9b18edea0c3533799069abc95c9c55c8607d)
Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.com>
---
 Documentation/ABI/stable/sysfs-bus-mhi | 21 +++++++++++++++
 MAINTAINERS                            |  1 +
 drivers/bus/mhi/core/init.c            | 37 ++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)
 create mode 100644 Documentation/ABI/stable/sysfs-bus-mhi

diff --git a/Documentation/ABI/stable/sysfs-bus-mhi b/Documentation/ABI/stable/sysfs-bus-mhi
new file mode 100644
index 000000000000..ecfe7662f8d0
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-bus-mhi
@@ -0,0 +1,21 @@
+What:		/sys/bus/mhi/devices/.../serialnumber
+Date:		Sept 2020
+KernelVersion:	5.10
+Contact:	Bhaumik Bhatt <bbhatt at codeaurora.org>
+Description:	The file holds the serial number of the client device obtained
+		using a BHI (Boot Host Interface) register read after at least
+		one attempt to power up the device has been done. If read
+		without having the device power on at least once, the file will
+		read all 0's.
+Users:		Any userspace application or clients interested in device info.
+
+What:		/sys/bus/mhi/devices/.../oem_pk_hash
+Date:		Sept 2020
+KernelVersion:	5.10
+Contact:	Bhaumik Bhatt <bbhatt at codeaurora.org>
+Description:	The file holds the OEM PK Hash value of the endpoint device
+		obtained using a BHI (Boot Host Interface) register read after
+		at least one attempt to power up the device has been done. If
+		read without having the device power on at least once, the file
+		will read all 0's.
+Users:		Any userspace application or clients interested in device info.
diff --git a/MAINTAINERS b/MAINTAINERS
index c8784acf6bd5..eed11d82df9a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10916,6 +10916,7 @@ M:	Hemant Kumar <hemantk at codeaurora.org>
 L:	linux-arm-msm at vger.kernel.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mani/mhi.git
+F:	Documentation/ABI/stable/sysfs-bus-mhi
 F:	Documentation/mhi/
 F:	drivers/bus/mhi/
 F:	include/linux/mhi.h
diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 61e5885a331a..a33665b7ee54 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -76,6 +76,42 @@ const char *to_mhi_pm_state_str(enum mhi_pm_state state)
 	return mhi_pm_state_str[index];
 }
 
+static ssize_t serial_number_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	struct mhi_device *mhi_dev = to_mhi_device(dev);
+	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
+
+	return snprintf(buf, PAGE_SIZE, "Serial Number: %u\n",
+			mhi_cntrl->serial_number);
+}
+static DEVICE_ATTR_RO(serial_number);
+
+static ssize_t oem_pk_hash_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct mhi_device *mhi_dev = to_mhi_device(dev);
+	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
+	int i, cnt = 0;
+
+	for (i = 0; i < ARRAY_SIZE(mhi_cntrl->oem_pk_hash); i++)
+		cnt += snprintf(buf + cnt, PAGE_SIZE - cnt,
+				"OEMPKHASH[%d]: 0x%x\n", i,
+				mhi_cntrl->oem_pk_hash[i]);
+
+	return cnt;
+}
+static DEVICE_ATTR_RO(oem_pk_hash);
+
+static struct attribute *mhi_dev_attrs[] = {
+	&dev_attr_serial_number.attr,
+	&dev_attr_oem_pk_hash.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(mhi_dev);
+
 /* MHI protocol requires the transfer ring to be aligned with ring length */
 static int mhi_alloc_aligned_ring(struct mhi_controller *mhi_cntrl,
 				  struct mhi_ring *ring,
@@ -1301,6 +1337,7 @@ struct bus_type mhi_bus_type = {
 	.dev_name = "mhi",
 	.match = mhi_match,
 	.uevent = mhi_uevent,
+	.dev_groups = mhi_dev_groups,
 };
 
 static int __init mhi_init(void)
-- 
2.29.2