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[PATCH] SPI: spi_butterfly, restore lost deltas

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This resolves some minor version skew glitches that accumulated for the AVR
Butterfly adapter driver, which caused among other things the existence of
a duplicate Kconfig entry.  Most of it boils down to comment updates, but in
one case it removes some now-superfluous code that would be better if not
copied into other controller-level drivers.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
This commit is contained in:
David Brownell
2006-01-21 13:21:43 -08:00
committed by Greg Kroah-Hartman
parent 022f7b07bf
commit 9c1da3cb46
3 changed files with 34 additions and 35 deletions
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23
Documentation/spi/butterfly
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@@ -12,13 +12,20 @@ You can make this adapter from an old printer cable and solder things
directly to the Butterfly. Or (if you have the parts and skills) you
can come up with something fancier, providing ciruit protection to the
Butterfly and the printer port, or with a better power supply than two
signal pins from the printer port.
signal pins from the printer port. Or for that matter, you can use
similar cables to talk to many AVR boards, even a breadboard.
This is more powerful than "ISP programming" cables since it lets kernel
SPI protocol drivers interact with the AVR, and could even let the AVR
issue interrupts to them. Later, your protocol driver should work
easily with a "real SPI controller", instead of this bitbanger.
The first cable connections will hook Linux up to one SPI bus, with the
AVR and a DataFlash chip; and to the AVR reset line. This is all you
need to reflash the firmware, and the pins are the standard Atmel "ISP"
connector pins (used also on non-Butterfly AVR boards).
connector pins (used also on non-Butterfly AVR boards). On the parport
side this is like "sp12" programming cables.
Signal Butterfly Parport (DB-25)
------ --------- ---------------
@@ -40,10 +47,14 @@ by clearing PORTB.[0-3]); (b) configure the mtd_dataflash driver; and
SELECT = J400.PB0/nSS = pin 17/C3,nSELECT
GND = J400.GND = pin 24/GND
The "USI" controller, using J405, can be used for a second SPI bus. That
would let you talk to the AVR over SPI, running firmware that makes it act
as an SPI slave, while letting either Linux or the AVR use the DataFlash.
There are plenty of spare parport pins to wire this one up, such as:
Or you could flash firmware making the AVR into an SPI slave (keeping the
DataFlash in reset) and tweak the spi_butterfly driver to make it bind to
the driver for your custom SPI-based protocol.
The "USI" controller, using J405, can also be used for a second SPI bus.
That would let you talk to the AVR using custom SPI-with-USI firmware,
while letting either Linux or the AVR use the DataFlash. There are plenty
of spare parport pins to wire this one up, such as:
Signal Butterfly Parport (DB-25)
------ --------- ---------------