On 7/30/22 00:54, Chetan Chinnadagudihundi Ravindranath (Consultant)
(QUIC) wrote:
> why a change is being made:
There are 2 variants of the android bootdev device. One is EMMC and
other is UFS. We would be not knowing the android boot storage type at
build time. So, we need to know the storage type at run time(bootup
time) by reading the "androidboot.bootdevice=". We need to distinguish
between EMMC and UFS at bootup time and take appropriate action.
> Information about why support is being added for the
androidboot.bootdevice parameter in the Qualcomm UFS host controller
driver:
We will get the "androidboot.bootdevice=" by reading cmdline
case 1: if the boot image header version is 3
We get the bootdevice info by reading /proc/cmdline (
__setup("androidboot.bootdevice=", get_android_boot_dev_v3);
Case 2: if the boot image header version is 4
We get the bootdevice info by reading /proc/bootconfig
(android_boot_dev_v4 = xbc_find_value("androidboot.bootdevice", &vnode))
Qualcomm UFS modules(ufs-qcom.c) calls this
get_storage_boot_device()(ufs-cmdline.c) and get the bootdevice info
and take appropriate action. This code is yet to be upstreamed. Please
let me know if this info convincing.
Instead of posting the above information on the linux-scsi mailing list,
it should be integrated in the description of the patch. Please do that
before reposting this patch and also make sure that the code that uses
this new kernel command line parameter is included in the same patch series.
Thanks,
Bart.
