On Tue, 2018-07-17 at 13:23 -0700, Evan Green wrote: +AD4- On Mon, Jul 16, 2018 at 5:04 PM Bart Van Assche +ADw-Bart.VanAssche+AEA-wdc.com+AD4- wrote: +AD4- +AD4- +AD4- +AD4- On Mon, 2018-07-16 at 16:46 -0700, Evan Green wrote: +AD4- +AD4- +AD4- I see Bart has chimed in on the next series with a suggestion to break +AD4- +AD4- +AD4- out each field into individual files within configfs. Bart, what are +AD4- +AD4- +AD4- your feelings about converting to a binary attribute? I remember when +AD4- +AD4- +AD4- I did my sysfs equivalent of this patch, somebody chimed in indicating +AD4- +AD4- +AD4- a +ACI-commit+ACI- file might be needed so that the new configuration could be +AD4- +AD4- +AD4- written in one fell swoop. One advantage of the binary attribute is +AD4- +AD4- +AD4- that it writes the configuration atomically. +AD4- +AD4- +AD4- +AD4- Hello Evan, +AD4- +AD4- +AD4- +AD4- I may be missing some UFS background information. But since a configfs interface +AD4- +AD4- is being added I think the same rule applies as to all Linux kernel user space +AD4- +AD4- interfaces, namely that it should be backwards compatible. Additionally, if +AD4- +AD4- anyone ever will want to use this interface from a shell script, I think that +AD4- +AD4- it will be much easier to write multiple ASCII attributes than a single binary +AD4- +AD4- attribute. +AD4- +AD4- +AD4- +AD4- Hi Bart, +AD4- I'm unsure about the compatibility aspect for binary attributes that +AD4- essentially represent direct windows into hardware. I suppose this +AD4- comes down to who this interface is most useful to. Hypothetically +AD4- lets say a future revision of UFS adds fields to the configuration +AD4- descriptor, but is otherwise backwards compatible. If this interface +AD4- is primarily for OEMs initializing their devices in the factory, then +AD4- I'd argue they'd want the most direct window to the configuration +AD4- descriptor. These folks probably just have a configuration they want +AD4- to plunk into the hardware, and would prefer being able to write all +AD4- fields over having some sort of compatibility restriction. If, on the +AD4- other hand, this is used by long-running scripts that stick around for +AD4- years without modification, then yes, it seems like it would be more +AD4- important to stay compatible, and have smarts in the kernel to make +AD4- writes of old descriptors work in new devices. +AD4- +AD4- At least for myself, I fall into the category of someone who just +AD4- needs to plunk a configuration descriptor in once, and would prefer +AD4- not to have to submit kernel changes if the descriptor evolves +AD4- slightly. It also seemed a little odd that this patch now spends a +AD4- bunch of energy converting ASCII into bytes, just to write it without +AD4- modification into the hardware, and convert back again to ASCII for +AD4- reads. +AD4- +AD4- We plan to use a script for provisioning, and could easily handle +AD4- ASCII or rawbytes: +AD4- +AD4- +ACM- Some bytes, ready to go with the interface today... +AD4- some+AF8-bytes+AD0AIg-00 01 02 03+ACI- +AD4- +AD4- +ACM- Same bytes, now in binary format +AD4- bytes+AF8-fmt+AD0AJA-(echo +ACI- +ACQ-some+AF8-bytes+ACI- +AHw- sed 's/ /+AFwAXA-x/g') +AD4- /usr/bin/printf +ACIAJA-bytes+AF8-fmt+ACI- +AD4- /configfs/ufs+AF8-provision +AD4- +AD4- I'm not dead set on binary, since as above I could do it either way, +AD4- but it seemed worth at least talking through. Let me know what you +AD4- think. The configfs documentation (Documentation/filesystems/configfs/configfs.txt) is clear about this: +ACI-Preferably only one value per file should be used.+ACI- So I would like to hear the opinion of someone who has more authority than I with regard to configfs. Bart.
