[PATCH] spi: misc fixes

This collects some small SPI patches that seem to be missing from the MM tree:

- spi_butterfly kbuild hooks got dropped somehow; this restores them
- quick fix for a (theoretical?) m25p80_write() oops noted by Andrew
- quick fix for a potential config-specific oops for mtd_dataflash()
- minor doc tweaks

Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/spi/spi-summary

···
    /sys/devices/.../CTLR/spiB.C ... spi_device for on bus "B",
 	chipselect C, accessed through CTLR.
 
+   /sys/devices/.../CTLR/spiB.C/modalias ... identifies the driver
+	that should be used with this device (for hotplug/coldplug)
+
    /sys/bus/spi/devices/spiB.C ... symlink to the physical
    	spiB-C device
 
···
 
 Like with other static board-specific setup, you won't unregister those.
 
+The widely used "card" style computers bundle memory, cpu, and little else
+onto a card that's maybe just thirty square centimeters.  On such systems,
+your arch/.../mach-.../board-*.c file would primarily provide information
+about the devices on the mainboard into which such a card is plugged.  That
+certainly includes SPI devices hooked up through the card connectors!
+
 
 NON-STATIC CONFIGURATIONS
 
···
 up the spi bus master, and will likely need spi_new_device() to provide the
 board info based on the board that was hotplugged.  Of course, you'd later
 call at least spi_unregister_device() when that board is removed.
+
+When Linux includes support for MMC/SD/SDIO/DataFlash cards through SPI, those
+configurations will also be dynamic.  Fortunately, those devices all support
+basic device identification probes, so that support should hotplug normally.
 
 
 How do I write an "SPI Protocol Driver"?

drivers/mtd/devices/m25p80.c

···
 
 			spi_sync(flash->spi, &m);
 
-			*retlen += m.actual_length - sizeof(flash->command);
+			if (retlen)
+				*retlen += m.actual_length
+					- sizeof(flash->command);
 	        }
  	}
 

drivers/mtd/devices/mtd_dataflash.c

···
 			priv->partitioned = 1;
 			return add_mtd_partitions(device, parts, nr_parts);
 		}
-	} else if (pdata->nr_parts)
+	} else if (pdata && pdata->nr_parts)
 		dev_warn(&spi->dev, "ignoring %d default partitions on %s\n",
 				pdata->nr_parts, device->name);
 

drivers/spi/Kconfig

···
 	  need it.  You only need to select this explicitly to support driver
 	  modules that aren't part of this kernel tree.
 
+config SPI_BUTTERFLY
+	tristate "Parallel port adapter for AVR Butterfly (DEVELOPMENT)"
+	depends on SPI_MASTER && PARPORT && EXPERIMENTAL
+	select SPI_BITBANG
+	help
+	  This uses a custom parallel port cable to connect to an AVR
+	  Butterfly <http://www.atmel.com/products/avr/butterfly>, an
+	  inexpensive battery powered microcontroller evaluation board.
+	  This same cable can be used to flash new firmware.
+
 #
 # Add new SPI master controllers in alphabetical order above this line
 #

drivers/spi/Makefile

···
 
 # SPI master controller drivers (bus)
 obj-$(CONFIG_SPI_BITBANG)		+= spi_bitbang.o
+obj-$(CONFIG_SPI_BUTTERFLY)		+= spi_butterfly.o
 # 	... add above this line ...
 
 # SPI protocol drivers (device/link on bus)