Hotplugging USB Compact flash reader

DISCUSSION Ajay 2 participants 3 messages Aug 9, 2002 – Aug 10, 2002

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Ajay

author

2002-08-09 04:40 UTC #0 lore raw

HI,
I am a first timer in this groups.
I am trying to develop something that can recognize when a USB Flash card reader is plugged in, when a media is plugged into the reader, and when either of them are removed. Something like plug and play - just plug in and an icon appears on the desktop which takes you to the diectory. I guess hotplugging should have the answer.
I read as much as I could but I can't figure out where /sbin/hotplug and usb.agent fit in. How do I trap the hotplug notification? Do I have to "register"? How do I do that?
Thanks and regards,
Ajay

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Ajay

author

2002-08-10 04:58 UTC #1 lore raw

I figured out enough of usb.agent to be able to trace it to a point where I found that the handbook and the userbook do not have a match for the VID-PID for the reader that I'm using (it's an SCM ORCA cf-ms-sm-sd reader). However I found that it loads (binds?) the correct drivers. So in the "add" event I simply added "mount /dev/sda /mnt/cf" and in the "remove" event I unmounted it. All this is in usb.agent.

In Gnome this works fine - an icon comes to the desktop without me having to do anything else. In KDE, there is no icon, but the device is mounted.

My question is:
1. Is it correct to modify usb.agent itself? Should I rather include the VID-PID and other details in the handbook/userbook?

2. What is the "match-flag"?? AFAI can see it seems to be a "mask flag" - something to be 'anded' with something else. What is the principle behind it?

3. This is premature, but could someone give me a hint as to which desktop agent I should be talking to?

Thanks and regards,
Ajay.
--- David Brownell <[email protected]> wrote: >

Quoted 74 lines · Ajay

Quoted 3 lines
HI,
I am a first timer in this groups.
I am trying to develop something that can
recognize
Quoted 2 lines
when a USB Flash card reader is plugged in, when a media is plugged into the reader, and when either
of
Quoted 1 line
them are removed. Something like plug and play -
just
Quoted 1 line
plug in and an icon appears on the desktop which
takes
Quoted 1 line
you to the diectory. I guess hotplugging should
have
Quoted 1 line
the answer.
You're asking about a missing piece, or maybe a
couple.
- "disk level" hotplug events, reporting new storage so that it can be mounted. in 2.5 it seems like at least the "scsi hotplug" may really happen,
which
should solve your USB cardreader issue.
- hotplug events talking to X11 desktops
UNIX desktops traditionally "knew" that only a few devices
might ever get new media, and polled things like diskette
and cdrom devices from some desktop monitoring program.
(Maybe not the same one polling for filesystem changes.)
Of Linux today, such devices can connect
dynamically, so
any "poll only these devices" architecture just
loses.
One of the KDE or GNOME object model hooks ought to do
nicely to let some hotplug agent talk to some service
running inside the desktop, reusing infrastructure that'd
otherwise need to be reinvented for a "raw X11" solution.
Quoted 1 line
I read as much as I could but I can't figure out
where
Quoted 1 line
/sbin/hotplug and usb.agent fit in. How do I trap
the
Quoted 1 line
hotplug notification? Do I have to "register"? How
do
Quoted 1 line
I do that?
Considering that you'd need to design some of the hotplug
events needed to address this problem, you'll need to
understand enough to create those answers yourself ... or
wait for someone else to address them! :)
The core observation will be that the hotplug agent for
some TBD "storage hotplug event" would need to invoke some
program that's permitted to talk to the relevant desktop
service, which would pop up your desktop icon.

Quoted 5 lines

- Dave

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Quoted 8 lines

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David Brownell

2002-08-10 19:49 UTC #2 lore raw

In reply to Ajay

Quoted 4 lines

1. Is it correct to modify usb.agent itself? Should I rather include the VID-PID and other details in the handbook/userbook?

Don't modify usb.agent, no ... /etc/hotplug/usb/$DRIVERNAME is where you put per-driver setup/config tweaks.

From what you said, you're assuming only one reader (or
SCSI-ish device) will ever be connected ... you're choosing a single device name and mount point. That's error prone; the reason is that you're using the wrong level of hotplug event. As I said earlier, to solve this safely you need higher level hotplug events: "here's a disk" (/dev/sdc or whatever).

Quoted 3 lines

2. What is the "match-flag"?? AFAI can see it seems to be a "mask flag" - something to be 'anded' with something else. What is the principle behind it?

See <linux/usb.h> for "struct usb_device_id" support.

Quoted 2 lines

3. This is premature, but could someone give me a hint as to which desktop agent I should be talking to?

To my knowledge, there is no such desktop agent yet. That's why I suggested you be prepared to write one.

- Dave