Re: [PATCH+RFC] sg: char_devs + seq_file lk2.6.0t6

[Douglas Gilbert <dougg@torque.net>]

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Douglas Gilbert wrote:
> Changes to scsi generic (sg) driver [gzipped patch against
> lk 2.6.0-test6]:
>     - add "struct cdev" [char_devs] objects to increase
>       maximum number of sg devices from 256 to 8192
>     - use seq_file interface for /proc/scsi/sg/*
>       pseudo files
> 
> The first change re-introduces sg devices into sysfs.
> Each sg device has a directory (currently empty)
> with a name of the form: "/sys/cdev/major/sg<n>". When I tried
> adding 280 scsi "devices" with scsi_debug all the expected
> sg directories appeared (sg0..sg279). However sd registered
> the first 256 "disks" (up to /dev/sdiv) and failed thereafter
> with error "-16" (is anybody working on extending sd's
> disk and partition range?).
> 
> Would it be possible to put a symbolic link in the
> /sys/cdev/major/sg<n> directory to the corresponding
> sysfs scsi device (and vice versa)?

Well nobody objected so attached is another patch on
sg (as found in lk 2.6.0-test7) that additionally sets
up two symlinks from /sys/cdev/major/sg<n> to the
corresponding scsi device in sysfs and back again. A
pruned sysfs "tree" is also attached to illustrate.

Now I need to find somewhere in sysfs to place sg's
driver attributes (e.g. "allow_dio"). char_devs seem
to be deficient in this respect.

Doug Gilbert


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.
|-- block
|   ...
|   |-- sda
|       |-- dev
|       |-- device -> ../../devices/pseudo_0/adapter0/host1/1:0:0:0
|       |-- queue
|        .......
|-- bus
|   ......
|   |-- pseudo
|   |   |-- devices
|   |   |   `-- adapter0 -> ../../../devices/pseudo_0/adapter0
|   |   `-- drivers
|   |       `-- scsi_debug
|   |           |-- adapter0 -> ../../../../devices/pseudo_0/adapter0
|   |           |-- add_host
|   |           .....
|   |-- scsi
|       |-- devices
|       |   `-- 1:0:0:0 -> ../../../devices/pseudo_0/adapter0/host1/1:0:0:0
|       `-- drivers
|           `-- sd
|               `-- 1:0:0:0 -> ../../../../devices/pseudo_0/adapter0/host1/1:0:0:0
|-- cdev
|   ....
|   |-- major
|       |-- sg0
|       |   `-- device -> ../../../devices/pseudo_0/adapter0/host1/1:0:0:0
|-- class
|   ...
|   |-- scsi_device
|   |   `-- 1:0:0:0
|   |       |-- device -> ../../../devices/pseudo_0/adapter0/host1/1:0:0:0
|   |       `-- driver -> ../../../bus/scsi/drivers/sd
|   |-- scsi_host
|       `-- host1
|           |-- cmd_per_lun
|           |-- device -> ../../../devices/pseudo_0/adapter0/host1
|           ....
|-- devices
    ....
    |-- pseudo_0
        |-- adapter0
            |-- detach_state
            |-- host1
                |-- 1:0:0:0
                    |-- block -> ../../../../../block/sda
                    |-- delete
                    |-- detach_state
                    |-- device_blocked
                    |-- generic -> ../../../../../cdev/major/sg0
                    .....