Merge tag 'docs-5.1' of git://git.lwn.net/linux

	dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,

		       dma_addr_t dma_handle, unsigned long attrs)

Free memory allocated by the dma_alloc_attrs().  All parameters common

parameters must identical to those otherwise passed to dma_fre_coherent,

Free memory allocated by the dma_alloc_attrs().  All common

parameters must be identical to those otherwise passed to dma_free_coherent,

and the attrs argument must be identical to the attrs passed to

dma_alloc_attrs().

dma-api/nr_total_entries	The total number of dma_debug_entries in the

				allocator, both free and used.

dma-api/driver-filter		You can write a name of a driver into this file

dma-api/driver_filter		You can write a name of a driver into this file

				to limit the debug output to requests from that

				particular driver. Write an empty string to

				that file to disable the filter and see

-------------------

To translate the virtual address to a bus address, use the normal DMA

API. Do _not_ use isa_virt_to_phys() even though it does the same

thing. The reason for this is that the function isa_virt_to_phys()

API. Do _not_ use isa_virt_to_bus() even though it does the same

thing. The reason for this is that the function isa_virt_to_bus()

will require a Kconfig dependency to ISA, not just ISA_DMA_API which

is really all you need. Remember that even though the DMA controller

has its origins in ISA it is used elsewhere.

So let's look at an example RCU lockdep splat from 3.0-rc5, one that

has long since been fixed:

===============================

[ INFO: suspicious RCU usage. ]

-------------------------------

=============================

WARNING: suspicious RCU usage

-----------------------------

block/cfq-iosched.c:2776 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 0

3 locks held by scsi_scan_6/1552:

 #0:  (&shost->scan_mutex){+.+.+.}, at: [<ffffffff8145efca>]

 #0:  (&shost->scan_mutex){+.+.}, at: [<ffffffff8145efca>]

scsi_scan_host_selected+0x5a/0x150

 #1:  (&eq->sysfs_lock){+.+...}, at: [<ffffffff812a5032>]

 #1:  (&eq->sysfs_lock){+.+.}, at: [<ffffffff812a5032>]

elevator_exit+0x22/0x60

 #2:  (&(&q->__queue_lock)->rlock){-.-...}, at: [<ffffffff812b6233>]

 #2:  (&(&q->__queue_lock)->rlock){-.-.}, at: [<ffffffff812b6233>]

cfq_exit_queue+0x43/0x190

stack backtrace:

Compiling the kernel

--------------------

 - Make sure you have at least gcc 3.2 available.

 - Make sure you have at least gcc 4.6 available.

   For more information, refer to :ref:`Documentation/process/changes.rst <changes>`.

   Please note that you can still run a.out user programs with this kernel.

			arch/x86/kernel/cpu/cpufreq/elanfreq.c.

	elevator=	[IOSCHED]

			Format: {"cfq" | "deadline" | "noop"}

			See Documentation/block/cfq-iosched.txt and

			Documentation/block/deadline-iosched.txt for details.

			Format: { "mq-deadline" | "kyber" | "bfq" }

			See Documentation/block/deadline-iosched.txt,

			Documentation/block/kyber-iosched.txt and

			Documentation/block/bfq-iosched.txt for details.

	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]

			Specifies physical address of start of kernel core

			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,

			the default is off.

	kpti=		[ARM64] Control page table isolation of user

			and kernel address spaces.

			Default: enabled on cores which need mitigation.

			0: force disabled

			1: force enabled

	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.

			Default is 0 (don't ignore, but inject #GP)