[Buildroot] UDEV Card reader

[Pablo Trujillo]

2009/11/17 Hedwin Koning <hedwin.koning at gmail.com>:
> Pablo Trujillo wrote:
>>
>> Hi everyone this is my first post I don't know if is correct to ask
>> this here, My natural idiom is not  English so sorry for mistakes:
>>
>> I was working with the buildroot around one year  and I'm very glad
>> for all its benefits to make a real small custom system.
>>
>> Im trying with the udev system (no the mdev that come with busybox).
>> But the thing is that i don't understand why no work with card readers
>> I was searching in google and I found this:
>>
>> http://shallowsky.com/blog/linux/udev-cardreaders-update.html
>>
>> I try that but nothing happen, I don't know why.
>>
>> if I put the compact flash and later I insert the reader , the system
>> detect the card, but if I plug first the reader and after I put the
>> CF, nothing happen, I mean the plug & unplug event seem not to work.
>>
>> If anyone can help me
>>
>> by the way :X86 architecture.
>>
>> regards
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>>
>>
>
> Hi
>
> The problem with cardreaders is is that when memory cards are inserted after
> the
> cardreader itself is inserted no events are sent to the kernel by the
> cardreader. To
> solve this you need
> to run  a background process that monitors insertion and removals of memory
> cards. The
> background process repeatingly tries to open the devices of the cardreader.
> Once it does
> the normal events (add, remove) are sent by the kernel which can be handled
> by either
> udev of mdev.
> In linux HAL takes care of this. If you try it on a linux machine you can
> see the background
> processes using ps. Once you have the process names you can easily find them
> back in the
> HAL source code.
>
> Hedwin Koning.
>
>
>
>
>
>

Thank you so much for you answer, yes actually after some
investigation I realise what happening,
eventually I made the process that take care of polling, each 2 or 3
second to  device.
But , for the nature of my project I needed some kind of advise to my
app to know when the card was inserted/removed.
As you say HAL take care of this in a Desktop Distribution, so with
this, I search the HAL source  code and I found that in it, when there
is no card
and the polling try to open the device, the errno variable is set to
NOMEDIUM, so HAL can notice that there is no card.
I use this condition too, and its works!

for the record: if someone ask : why don't you use HAL any way?, the
answer : because is too big and I just need some features, not the
whole system.

Thank you Again!