[bitbash] Add optional open() and close() methods for bit-bashing interfaces

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/bitbash/i2c_bit.c

 	 * pull SDA low while SCL is high (which creates a start
 	 * condition).
 	 */
+	open_bit ( basher );
 	setscl ( basher, 0 );
 	setsda ( basher, 1 );
 	for ( i = 0 ; i < I2C_RESET_MAX_CYCLES ; i++ ) {
 			i2c_stop ( basher );
 			DBGC ( basher, "I2CBIT %p reset after %d attempts\n",
 			       basher, ( i + 1 ) );
+			close_bit ( basher );
 			return 0;
 		}
 		setscl ( basher, 0 );
 
 	DBGC ( basher, "I2CBIT %p could not reset after %d attempts\n",
 	       basher, i );
+	close_bit ( basher );
 	return -ETIMEDOUT;
 }
 
 	DBGC ( basher, "I2CBIT %p reading from device %x: ",
 	       basher, i2cdev->dev_addr );
 
+	open_bit ( basher );
+
 	for ( ; ; data++, offset++ ) {
 
 		/* Select device for writing */
 	
 	DBGC ( basher, "%s\n", ( rc ? "failed" : "" ) );
 	i2c_stop ( basher );
+	close_bit ( basher );
 	return rc;
 }
 
 	DBGC ( basher, "I2CBIT %p writing to device %x: ",
 	       basher, i2cdev->dev_addr );
 
+	open_bit ( basher );
+
 	for ( ; ; data++, offset++ ) {
 
 		/* Select device for writing */
 		if ( ( rc = i2c_send_byte ( basher, *data ) ) != 0 )
 			break;
 	}
-	
+
 	DBGC ( basher, "%s\n", ( rc ? "failed" : "" ) );
 	i2c_stop ( basher );
+	close_bit ( basher );
 	return rc;
 }
 

src/drivers/bitbash/spi_bit.c

 	uint32_t tmp_address;
 	uint32_t tmp_address_detect;
 
+	/* Open bit-bashing interface */
+	open_bit ( &spibit->basher );
+
 	/* Deassert chip select to reset specified slave */
 	spi_bit_set_slave_select ( spibit, device->slave, DESELECT_SLAVE );
 
 	/* Deassert chip select on specified slave */
 	spi_bit_set_slave_select ( spibit, device->slave, DESELECT_SLAVE );
 
+	/* Close bit-bashing interface */
+	close_bit ( &spibit->basher );
+
 	return 0;
 }
 

src/include/ipxe/bitbash.h

 
 /** Bit-bashing operations */
 struct bit_basher_operations {
+	/**
+	 * Open bit-bashing interface (optional)
+	 *
+	 * @v basher		Bit-bashing interface
+	 */
+	void ( * open ) ( struct bit_basher *basher );
+	/**
+	 * Close bit-bashing interface (optional)
+	 *
+	 * @v basher		Bit-bashing interface
+	 */
+	void ( * close ) ( struct bit_basher *basher );
 	/**
 	 * Set/clear output bit
 	 *
 	struct bit_basher_operations *op;
 };
 
+/**
+ * Open bit-bashing interface
+ *
+ * @v basher		Bit-bashing interface
+ */
+static inline void open_bit ( struct bit_basher *basher ) {
+	if ( basher->op->open )
+		basher->op->open ( basher );
+}
+
+/**
+ * Close bit-bashing interface
+ *
+ * @v basher		Bit-bashing interface
+ */
+static inline void close_bit ( struct bit_basher *basher ) {
+	if ( basher->op->close )
+		basher->op->close ( basher );
+}
+
 extern void write_bit ( struct bit_basher *basher, unsigned int bit_id,
 			unsigned long data );
 extern int read_bit ( struct bit_basher *basher, unsigned int bit_id );