From: Andrew Lunn <andrew@lunn.ch>
To: Frank Pagliughi <fpagliughi@mindspring.com>
Cc: eCos Discussion <ecos-discuss@ecos.sourceware.org>
Subject: Re: [ECOS] Device driver open & close
Date: Wed, 27 Aug 2008 07:12:00 -0000 [thread overview]
Message-ID: <20080827052125.GB25863@lunn.ch> (raw)
In-Reply-To: <48B47309.8090608@mindspring.com>
>> This gets called for each open?
Yes. Take a look at the code:
io/fileio/current/src/devfs.cxx:dev_open() calls cyg_io_lookup() on
the device. And then there is this comment:
//
// Look up the devtab entry for a named device and return its handle.
// If the device is found and it has a "lookup" function, call that
// function to allow the device/driver to perform any necessary
// initializations.
//
Cyg_ErrNo
cyg_io_lookup(const char *name, cyg_io_handle_t *handle)
>>> You might be better using cyg_io_set_config() mechanism to turn it on
>>> and off.
>>>
>> This is unfortunate. For another example, the system will have the
>> ability to power down the compact flash drive(s). Which order should
>> the power down happen?
>> flush() the buffers, then cyg_io_set_config() to power down the
>> drive, *then* close() ? I assume you can't use the handle to
>> set_config after the close(). Right?
File systems work differently. There you have a clean mount and
unmount. So i would extend the mount and umount call to call the
cyg_io_set_config() to power the device up/down. However you might
have a problem with the partition table,
> I'm just doing the OS port & device drivers for a board that has to
> really conserve power and thus turn devices off and on a lot. Someone
> else will write the application, so I'm trying to make the interface as
> simple and familiar as possible (therefore standard I/O api). It seems
> that the eCos device API assumes that devices will be initialized then
> stay on forever. So, any ideas are appreciated.
Well LCD devices don't always follow standard I/O. This is especially
true if you are doing a windowing driver? Or is it plain text. And
how is the driver structured? Maybe you maintain a frame buffer in
local memory and blit it out to the LCD every so often? With the
cyg_io_set_config() you can keep the frame buffer running all the time
and use the cyg_io_set_config() to power up/down the LCD controller
and start/stop blitting. Another cyg_io_set_config() would control the
backlight etc.
Andrew
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prev parent reply other threads:[~2008-08-27 5:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-26 4:49 Frank Pagliughi
2008-08-26 15:28 ` Andrew Lunn
2008-08-26 21:20 ` Frank Pagliughi
2008-08-27 5:22 ` Frank Pagliughi
2008-08-27 7:12 ` Andrew Lunn [this message]
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