spi: add advanced open function with 32-bit extra flags

sgjava · Dec 16, 2020 · 56755ac · 56755ac
1 parent 28ab557
commit 56755ac
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Showing 3 changed files with 49 additions and 0 deletions.
diff --git a/docs/spi.md b/docs/spi.md
@@ -12,6 +12,8 @@ spi_t *spi_new(void);
 int spi_open(spi_t *spi, const char *path, unsigned int mode, uint32_t max_speed);
 int spi_open_advanced(spi_t *spi, const char *path, unsigned int mode, uint32_t max_speed,
                       spi_bit_order_t bit_order, uint8_t bits_per_word, uint8_t extra_flags);
+int spi_open_advanced2(spi_t *spi, const char *path, unsigned int mode, uint32_t max_speed,
+                       spi_bit_order_t bit_order, uint8_t bits_per_word, uint32_t extra_flags);
 int spi_transfer(spi_t *spi, const uint8_t *txbuf, uint8_t *rxbuf, size_t len);
 int spi_close(spi_t *spi);
 void spi_free(spi_t *spi);
@@ -81,6 +83,18 @@ Returns 0 on success, or a negative [SPI error code](#return-value) on failure.
 
 ------
 
+``` c
+int spi_open_advanced2(spi_t *spi, const char *path, unsigned int mode, uint32_t max_speed,
+                       spi_bit_order_t bit_order, uint8_t bits_per_word, uint32_t extra_flags);
+```
+Open the `spidev` device at the specified path, with the specified SPI mode, max speed in hertz, bit order, bits per word, and extra flags. This open function is the same as `spi_open_advanced()`, except that `extra_flags` can be 32-bits.
+
+`spi` should be a valid pointer to an allocated SPI handle structure. SPI mode can be 0, 1, 2, or 3. Bit order can be `MSB_FIRST` or `LSB_FIRST`, as defined [above](#enumerations). Bits per word specifies the transfer word size. Extra flags specified additional flags bitwise-ORed with the SPI mode.
+
+Returns 0 on success, or a negative [SPI error code](#return-value) on failure.
+
+------
+
 ``` c
 int spi_transfer(spi_t *spi, const uint8_t *txbuf, uint8_t *rxbuf, size_t len);
 ```

diff --git a/src/spi.c b/src/spi.c
@@ -68,13 +68,22 @@ int spi_open(spi_t *spi, const char *path, unsigned int mode, uint32_t max_speed
 }
 
 int spi_open_advanced(spi_t *spi, const char *path, unsigned int mode, uint32_t max_speed, spi_bit_order_t bit_order, uint8_t bits_per_word, uint8_t extra_flags) {
+    return spi_open_advanced2(spi, path, mode, max_speed, bit_order, bits_per_word, extra_flags);
+}
+
+int spi_open_advanced2(spi_t *spi, const char *path, unsigned int mode, uint32_t max_speed, spi_bit_order_t bit_order, uint8_t bits_per_word, uint32_t extra_flags) {
+    uint32_t data32;
     uint8_t data8;
 
     /* Validate arguments */
     if (mode & ~0x3)
         return _spi_error(spi, SPI_ERROR_ARG, 0, "Invalid mode (can be 0,1,2,3)");
     if (bit_order != MSB_FIRST && bit_order != LSB_FIRST)
         return _spi_error(spi, SPI_ERROR_ARG, 0, "Invalid bit order (can be MSB_FIRST,LSB_FIRST)");
+#ifndef SPI_IOC_WR_MODE32
+    if (extra_flags > 0xff)
+        return _spi_error(spi, SPI_ERROR_UNSUPPORTED, "Kernel version does not support 32-bit SPI mode flags");
+#endif
 
     memset(spi, 0, sizeof(spi_t));
 
@@ -83,13 +92,36 @@ int spi_open_advanced(spi_t *spi, const char *path, unsigned int mode, uint32_t
         return _spi_error(spi, SPI_ERROR_OPEN, errno, "Opening SPI device \"%s\"", path);
 
     /* Set mode, bit order, extra flags */
+#ifndef SPI_IOC_WR_MODE32
     data8 = mode | ((bit_order == LSB_FIRST) ? SPI_LSB_FIRST : 0) | extra_flags;
     if (ioctl(spi->fd, SPI_IOC_WR_MODE, &data8) < 0) {
         int errsv = errno;
         close(spi->fd);
         spi->fd = -1;
         return _spi_error(spi, SPI_ERROR_CONFIGURE, errsv, "Setting SPI mode");
     }
+#else
+    if (extra_flags > 0xff) {
+        /* Use 32-bit mode if extra_flags is wider than 8-bits */
+        data32 = mode | ((bit_order == LSB_FIRST) ? SPI_LSB_FIRST : 0) | extra_flags;
+        if (ioctl(spi->fd, SPI_IOC_WR_MODE32, &data32) < 0) {
+            int errsv = errno;
+            close(spi->fd);
+            spi->fd = -1;
+            return _spi_error(spi, SPI_ERROR_CONFIGURE, errsv, "Setting SPI mode");
+        }
+    } else {
+        /* Prefer 8-bit mode, in case this library is inadvertently used on an
+         * older kernel. */
+        data8 = mode | ((bit_order == LSB_FIRST) ? SPI_LSB_FIRST : 0) | extra_flags;
+        if (ioctl(spi->fd, SPI_IOC_WR_MODE, &data8) < 0) {
+            int errsv = errno;
+            close(spi->fd);
+            spi->fd = -1;
+            return _spi_error(spi, SPI_ERROR_CONFIGURE, errsv, "Setting SPI mode");
+        }
+    }
+#endif
 
     /* Set max speed */
     if (ioctl(spi->fd, SPI_IOC_WR_MAX_SPEED_HZ, &max_speed) < 0) {

diff --git a/src/spi.h b/src/spi.h
@@ -38,6 +38,9 @@ int spi_open(spi_t *spi, const char *path, unsigned int mode,
 int spi_open_advanced(spi_t *spi, const char *path, unsigned int mode,
                         uint32_t max_speed, spi_bit_order_t bit_order,
                         uint8_t bits_per_word, uint8_t extra_flags);
+int spi_open_advanced2(spi_t *spi, const char *path, unsigned int mode,
+                       uint32_t max_speed, spi_bit_order_t bit_order,
+                       uint8_t bits_per_word, uint32_t extra_flags);
 int spi_transfer(spi_t *spi, const uint8_t *txbuf, uint8_t *rxbuf, size_t len);
 int spi_close(spi_t *spi);
 void spi_free(spi_t *spi);