spi: Split bus and I/O locking

The current SPI code attempts to use bus_lock_mutex for two purposes. One
is to implement spi_bus_lock() which grants exclusive access to the bus.
The other is to serialize access to the physical hardware. This duplicate
purpose causes confusion which leads to cases where access is not locked
when a caller holds the bus lock mutex. Fix this by splitting out the I/O
functionality into a new io_mutex.

This means taking both mutexes in the DMA path, replacing the existing
mutex with the new I/O one in the message pump (the mutex now always
being taken in the message pump) and taking the bus lock mutex in
spi_sync(), allowing __spi_sync() to have no mutex handling.

While we're at it hoist the mutex further up the message pump before we
power up the device so that all power up/down of the block is covered by
it and there are no races with in-line pumping of messages.

Reported-by: Rich Felker <dalias@libc.org>
Tested-by: Rich Felker <dalias@libc.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

path: root/ipv6.h

#ifndef IPV6_H
#define IPV6_H

#include <asm/byteorder.h>

#include "built_in.h"

/*
 * IPv6 fixed header
 *
 * BEWARE, it is incorrect. The first 4 bits of flow_lbl
 * are glued to priority now, forming "class".
 */
struct ipv6hdr {
#if defined(__LITTLE_ENDIAN_BITFIELD)
	__extension__ uint8_t priority:4,
			      version:4;
#elif defined(__BIG_ENDIAN_BITFIELD)
	__extension__ uint8_t version:4,
			      priority:4;
#else
# error "Please fix <asm/byteorder.h>"
#endif
	uint8_t flow_lbl[3];
	uint16_t payload_len;
	uint8_t nexthdr;
	uint8_t hop_limit;
	struct in6_addr saddr;
	struct in6_addr daddr;
} __packed;

#endif /* IPV6_H */