Messages in this thread | | | Date | Mon, 7 Aug 2017 09:23:27 -0700 | From | Bjorn Andersson <> | Subject | Re: [PATCH v2 4/5] soc: qcom: Remote FS memory driver |
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On Sat 05 Aug 02:58 PDT 2017, Christoph Hellwig wrote:
> On Wed, Aug 02, 2017 at 07:57:53PM -0700, Bjorn Andersson wrote: > > The rfsa driver is used for allocating and exposing regions of shared > > memory with remote processors for the purpose of exchanging sector-data > > between the remote filesystem service and its clients. > > Please explain which remote fs this is for, and submit said file system > for inclu??ion. >
In the NAND-era of Qualcomm platforms the modem firmware had direct access to the storage media, but with the move to eMMC and the transition of Linux/Android to become the "primary OS" this access was lost.
Remaining in the modem firmware is a file system (EFS) for parameter storage et al, but the block layer was replaced with a block-access protocol, "conveniently" called RemoteFS.
The protocol is based on a chunk of RAM and a set of messages to transfer sector-data between the storage device and the chunk of RAM.
Up until this patch the user space tool that implements the message handler just mapped the reserved memory region though /dev/mem, but this requires /dev/mem access and for the later platforms we need to make a call into TrustZone to provide the remote permission to access this memory region. So we need some code in the kernel to represent this.
> Else: NAK as the scheme looks completely brain dead and bonkers.
I can rework the commit message in an attempt to better explain the setup and hope you/people find it slightly less bonkers.
Does this sound reasonable?
Regards, Bjorn
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