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    Subject[PATCH 15/18] bus: mhi: core: Introduce sysfs entries for MHI
    Date
    From: Bhaumik Bhatt <bbhatt@codeaurora.org>

    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.

    Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
    Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
    Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
    ---
    Documentation/ABI/stable/sysfs-bus-mhi | 21 ++++++++++
    MAINTAINERS | 1 +
    drivers/bus/mhi/core/init.c | 53 ++++++++++++++++++++++++++
    3 files changed, 75 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@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@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 deaafb617361..11e7be9b9163 100644
    --- a/MAINTAINERS
    +++ b/MAINTAINERS
    @@ -11323,6 +11323,7 @@ M: Hemant Kumar <hemantk@codeaurora.org>
    L: linux-arm-msm@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..1b4161eaf0d8 100644
    --- a/drivers/bus/mhi/core/init.c
    +++ b/drivers/bus/mhi/core/init.c
    @@ -76,6 +76,56 @@ 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_sysfs_attrs[] = {
    + &dev_attr_serial_number.attr,
    + &dev_attr_oem_pk_hash.attr,
    + NULL,
    +};
    +
    +static const struct attribute_group mhi_sysfs_group = {
    + .attrs = mhi_sysfs_attrs,
    +};
    +
    +static int mhi_create_sysfs(struct mhi_controller *mhi_cntrl)
    +{
    + return sysfs_create_group(&mhi_cntrl->mhi_dev->dev.kobj,
    + &mhi_sysfs_group);
    +}
    +
    +static void mhi_destroy_sysfs(struct mhi_controller *mhi_cntrl)
    +{
    + sysfs_remove_group(&mhi_cntrl->mhi_dev->dev.kobj, &mhi_sysfs_group);
    +}
    +
    /* 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,
    @@ -917,6 +967,8 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
    mhi_cntrl->mhi_dev = mhi_dev;

    mhi_create_debugfs(mhi_cntrl);
    + if (mhi_create_sysfs(mhi_cntrl))
    + dev_err(mhi_cntrl->cntrl_dev, "Failed to create sysfs entries\n");

    return 0;

    @@ -940,6 +992,7 @@ void mhi_unregister_controller(struct mhi_controller *mhi_cntrl)
    struct mhi_chan *mhi_chan = mhi_cntrl->mhi_chan;
    unsigned int i;

    + mhi_destroy_sysfs(mhi_cntrl);
    mhi_destroy_debugfs(mhi_cntrl);

    kfree(mhi_cntrl->mhi_cmd);
    --
    2.17.1
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