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

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

[Douglas Gilbert]

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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)?

Doug Gilbert

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

[Douglas Gilbert]

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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
                    .....

[PATCH+RFC] sg: char_devs + seq_file lk2.6.0t9

[Douglas Gilbert]

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This is an updated patch for the sg driver that takes into
account Patrick LaVarre's fix for negative reserved buffer
sizes found in lk 2.6.0-test9.

So it has the same changelog to the patch I sent on 2003/10/11:
      - 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
      - sysfs symlinks between the sysfs scsi device and the
        corresponding sg cdev node (and vice versa)

An edited "tree" output showing an example of these symlinks
was included in my previous post.

As noted in another thread, st (and osst) may need "cdevs"
and sysfs symlinks so SCSI tape devices have sysfs visibility
in lk 2.6 .

Also if both st and sg had sysfs visibility then Patrick
Mansfield's scsi_id program could be made to work for tape
drives (enclosures, tape robots, etc) by following these
symlinks.

Doug Gilbert

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