Re: [ECOS] File system + block device drivers

[Jonathan Larmour <jlarmour at redhat dot com>]

Jurica Baricevic wrote:
> 
> Hi!
> 
> I should port an existing file system to eCos. After glancing eCos FS
> support sources I have noticed a few issues, which I would like to discuss:
> 
> 1. Current directory (getcwd, chdir)
> Is the current directory on eCos designed to be tracked per each thread
> independently?

Nope. POSIX says it's per "process" so that's essentially global in eCos.

> If so, is this the responsibility of the eCos file system
> manager (upper layer) or underlying file system implementations?

It's the responsibility of the fileio layer, although the FS needs to be
involved and is notified.

> 2. Block device driver
> As far as I could see, eCos still hasn't got complete block device
> interface. Namely, it seems that the following issues are not yet
> supported/defined:
> - request handling policy (access via sectors, scatter-gather list (?))
> - block device geometry. In particular: sectors, sector size, device size,
> physical format ioctl etc.
> - removable block devices (egg. check_media_change, revalidate)
> - partitionable block devices (egg. /dev/hda => /dev/hda1, dev/hda2)
> 
> Is there any current work in that direction?  If not, is there any publicly
> available framework/document/model/policy on the block device drivers
> development?

Nothing has been standardized yet, nor are we working on it internally at
this time. If you want to make a proposal, please do. Note that things like
the geometry could be obtained using cyg_io_get_config calls. And we don't
want to insert an extra layer of abstraction that would affect non block
devices.

Jifl
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