[PATCH] SPI: devices can require LSB-first encodings

[linux-2.6] / drivers / spi / spi_bitbang.c

diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 0525c99118c325615490ac38df474ddec5baa219..0f7f5c64391cbb62700189d6c2cc89220811421e 100644 (file)
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -138,8 +138,7 @@ static unsigned bitbang_txrx_32(
        return t->len - count;
 }
 
-static int
-bitbang_transfer_setup(struct spi_device *spi, struct spi_transfer *t)
+int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
 {
        struct spi_bitbang_cs   *cs = spi->controller_state;
        u8                      bits_per_word;
@@ -174,6 +173,7 @@ bitbang_transfer_setup(struct spi_device *spi, struct spi_transfer *t)
 
        return 0;
 }
+EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
 
 /**
  * spi_bitbang_setup - default setup for per-word I/O loops
@@ -187,13 +187,22 @@ int spi_bitbang_setup(struct spi_device *spi)
        if (!spi->max_speed_hz)
                return -EINVAL;
 
+       bitbang = spi_master_get_devdata(spi->master);
+
+       /* REVISIT: some systems will want to support devices using lsb-first
+        * bit encodings on the wire.  In pure software that would be trivial,
+        * just bitbang_txrx_le_cphaX() routines shifting the other way, and
+        * some hardware controllers also have this support.
+        */
+       if ((spi->mode & SPI_LSB_FIRST) != 0)
+               return -EINVAL;
+
        if (!cs) {
                cs = kzalloc(sizeof *cs, SLAB_KERNEL);
                if (!cs)
                        return -ENOMEM;
                spi->controller_state = cs;
        }
-       bitbang = spi_master_get_devdata(spi->master);
 
        if (!spi->bits_per_word)
                spi->bits_per_word = 8;
@@ -203,7 +212,7 @@ int spi_bitbang_setup(struct spi_device *spi)
        if (!cs->txrx_word)
                return -EINVAL;
 
-       retval = bitbang_transfer_setup(spi, NULL);
+       retval = spi_bitbang_setup_transfer(spi, NULL);
        if (retval < 0)
                return retval;
 
@@ -454,7 +463,9 @@ int spi_bitbang_start(struct spi_bitbang *bitbang)
                bitbang->use_dma = 0;
                bitbang->txrx_bufs = spi_bitbang_bufs;
                if (!bitbang->master->setup) {
-                       bitbang->setup_transfer = bitbang_transfer_setup;
+                       if (!bitbang->setup_transfer)
+                               bitbang->setup_transfer =
+                                        spi_bitbang_setup_transfer;
                        bitbang->master->setup = spi_bitbang_setup;
                        bitbang->master->cleanup = spi_bitbang_cleanup;
                }