Hi,
My usecase is enabling boot slot switching on Android A/B devices, where
the active LUN has to be changed in order to facilitate e.g. dual-booting
Android and mainline Linux. A similar interface is exposed by Android,
albeit
via ioctl. I've tested this patch and confirmed it enabled the necessary
functionality.
On 25/05/2022 21:34, Avri Altman wrote:
Hi,
Expands sysfs boot_lun attribute to be writable. Necessary to enable
proper support for LUN switching on some UFS devices.
Can you please elaborate why is it necessary?
What use case are you running?
Signed-off-by: Nia Espera <a5b6@xxxxxxxxxx>
---
drivers/scsi/ufs/ufs-sysfs.c | 67 +++++++++++++++++++++++++++++++++++-
1 file changed, 66 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/ufs/ufs-sysfs.c b/drivers/scsi/ufs/ufs-sysfs.c
index 5c405ff7b6ea..7bf5d6c3d0ec 100644
--- a/drivers/scsi/ufs/ufs-sysfs.c
+++ b/drivers/scsi/ufs/ufs-sysfs.c
@@ -1047,6 +1047,71 @@ static inline bool ufshcd_is_wb_attrs(enum attr_idn
idn)
idn <= QUERY_ATTR_IDN_CURR_WB_BUFF_SIZE;
}
+static ssize_t boot_lun_enabled_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct ufs_hba *hba = dev_get_drvdata(dev);
+ u32 slot;
+ int ret;
+ u8 index = 0;
+
+ down(&hba->host_sem);
+ if (!ufshcd_is_user_access_allowed(hba)) {
+ up(&hba->host_sem);
+ return -EBUSY;
+ }
+ if (ufshcd_is_wb_attrs(QUERY_ATTR_IDN_BOOT_LU_EN))
Clearly bBootLunEn is not a WB attribute.
+ index = ufshcd_wb_get_query_index(hba);
+ ufshcd_rpm_get_sync(hba);
+
+ ret = ufshcd_query_attr(hba, UPIU_QUERY_OPCODE_READ_ATTR,
+ QUERY_ATTR_IDN_BOOT_LU_EN, index, 0, &slot);
+
+ ufshcd_rpm_put_sync(hba);
+ if (ret) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = sysfs_emit(buf, "0x%08X\n", slot);
+out:
+ up(&hba->host_sem);
+ return ret;
+}
+
+static ssize_t boot_lun_enabled_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct ufs_hba *hba = dev_get_drvdata(dev);
+ u32 slot;
+ int ret;
+ u8 index = 0;
+
+ if (kstrtouint(buf, 0, &slot) < 0)
+ return -EINVAL;
You need to verify that no one set bBootLunEn = 0x0 because the device won't boot.
Better check explicitly that slot != bBootLunEn and its either 1 or 2.
Thanks,
Avri
+
+ down(&hba->host_sem);
+ if (!ufshcd_is_user_access_allowed(hba)) {
+ up(&hba->host_sem);
+ return -EBUSY;
+ }
+ if (ufshcd_is_wb_attrs(QUERY_ATTR_IDN_BOOT_LU_EN))
+ index = ufshcd_wb_get_query_index(hba);
+ ufshcd_rpm_get_sync(hba);
+
+ ret = ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_WRITE_ATTR,
+ QUERY_ATTR_IDN_BOOT_LU_EN, index, 0, &slot);
+ ufshcd_rpm_put_sync(hba);
+ if (ret) {
+ ret = -EINVAL;
+ goto out;
+ }
+out:
+ up(&hba->host_sem);
+ return ret ? ret : count;
+}
+
#define UFS_ATTRIBUTE(_name, _uname) \
static ssize_t _name##_show(struct device *dev, \
struct device_attribute *attr, char *buf) \
@@ -1077,8 +1142,8 @@ out: \
return ret; \
} \
static DEVICE_ATTR_RO(_name)
+static DEVICE_ATTR_RW(boot_lun_enabled);
-UFS_ATTRIBUTE(boot_lun_enabled, _BOOT_LU_EN);
UFS_ATTRIBUTE(max_data_size_hpb_single_cmd, _MAX_HPB_SINGLE_CMD);
UFS_ATTRIBUTE(current_power_mode, _POWER_MODE);
UFS_ATTRIBUTE(active_icc_level, _ACTIVE_ICC_LVL);
--
2.36.1
