PCI_MSI(9) | Kernel Developer's Manual | PCI_MSI(9) |
pci_msi
, pci_msix
,
pci_msi_count
, pci_msi_alloc
,
pci_msi_alloc_exact
,
pci_msix_count
,
pci_msix_alloc
,
pci_msix_alloc_exact
,
pci_msix_alloc_map
,
pci_intx_alloc
,
pci_intr_alloc
,
pci_intr_release
,
pci_intr_type
—
pci_msi_count
(pci_chipset_tag_t
pc, pcitag_t tag);
int
pci_msi_alloc
(const
struct pci_attach_args *pa,
pci_intr_handle_t **ihps,
int *count);
int
pci_msi_alloc_exact
(const
struct pci_attach_args *pa,
pci_intr_handle_t **ihps,
int count);
int
pci_msix_count
(pci_chipset_tag_t
pc, pcitag_t
tag);
int
pci_msix_alloc
(const
struct pci_attach_args *pa,
pci_intr_handle_t **ihps,
int *count);
int
pci_msix_alloc_exact
(const
struct pci_attach_args *pa,
pci_intr_handle_t **ihps,
int count);
int
pci_msix_alloc_map
(const
struct pci_attach_args *pa,
pci_intr_handle_t **ihps,
u_int *table_indexes,
int count);
int
pci_intx_alloc
(const
struct pci_attach_args *pa,
pci_intr_handle_t
**ihp);
int
pci_intr_alloc
(const
struct pci_attach_args *pa,
pci_intr_handle_t **ihp,
int *counts,
pci_intr_type_t
max_type);
void
pci_intr_release
(pci_chipset_tag_t
pc, pci_intr_handle_t
*pih, int
count);
pci_intr_type_t
pci_intr_type
(pci_chipset_tag_t
pc, pci_intr_handle_t
ih);
pci_msi
functions exist to allow device drivers to
use MSI/MSI-X. When the system uses MSI/MSI-X, it must define the
__HAVE_PCI_MSI_MSIX
build option.
Each driver has an attach
() function which
has a bus-specific attach_args structure. Each driver
for a PCI device is passed a pointer to an object of type
struct pci_attach_args which contains, among other
things, information about the location of the device in the PCI bus topology
sufficient to allow interrupts from the device to be handled.
pci_msi_count
() returns the max number of
the device's MSI. If the device can not use MSI,
pci_msi_count
() returns zero.
pci_msix_count
() works in the same manner for
MSI-X.
If a driver wishes to establish an MSI handler for the device, it
should pass the struct pci_attach_args * and
count pci_msi_alloc
() or
pci_msi_alloc_exact
() functions, which return zero
on success, and nonzero on failure. When the functions are successful, they
return the pointer to the allocated handle array in
pihs whose size is count or
less. The difference between pci_msi_alloc
() and
pci_msi_alloc_exact
() is whether
count can be decremented or not.
pci_msi_alloc
() can decrement
count, and which is similar to
FreeBSD's pci_alloc_msi
().
In contrast, pci_msi_alloc_exact
() can not decrement
count.
If the driver wishes to refer to the MSI source in an attach or
error message, it should use the value returned by
pci_intr_string
() the same as INTx. The buffer
passed to pci_intr_string
() should be at least
PCI_INTRSTR_LEN
bytes long.
Subsequently, when the driver is prepared to receive MSIs, it
should call pci_intr_establish
() the same as INTx to
actually establish the handler; when the device interrupts,
intrhand will be called with a single argument
intrarg, and will run at the interrupt priority level
ipl.
The return value of pci_intr_establish
()
may be saved and passed to pci_intr_disestablish
()
to disable the interrupt handler the same as INTx when the driver is no
longer interested in MSIs from the device. After that, the driver should
also call pci_intr_release
() to free resources about
MSI as well as INTx and MSI-X. If pih is NULL,
pci_intr_release
() does nothing.
If a driver wishes to establish an MSI-X handler for the device,
it is almost the same as MSI. The only differences is
pci_msix_alloc_map
(). This function can assign
separate handlers for each MSI-X table entry. I.e., if the driver wants to
assign the handlers in the following way:
msix_handler0 => MSI-X table index: 4 msix_handler1 => MSI-X table index: 5 msix_handler2 => MSI-X table index: 0
table_indexes[0] = 4; table_indexes[1] = 5; table_indexes[2] = 0;
If the driver wants to fall back to INTx, the driver should use
pci_intx_alloc
() and
pci_intr_release
() instead of
pci_intr_map
() to resolve contradiction of the
interrupt handler ownership. I.e., pci_intr_map
()
does not have the ownership (the function just calculates value), in
contrast, pci_msi_alloc
() and
pci_msix_alloc
() have (the functions allocate memory
for interrupt handlers).
pci_intr_alloc
() is wrapper function which
select and automatically fallback allocation functions according to the
argument counts. The elements of
counts array means each required interrupt count for
INTx, MSI, and MSI-X. The index count of counts must
be PCI_INTR_TYPE_SIZE
.
max_type must be
PCI_INTR_TYPE_MSIX
,
PCI_INTR_TYPE_MSI
, or
PCI_INTR_TYPE_INTX
. The parameter does not mean
array index counts of counts. The parameter means the
interrupt type which pci_intr_alloc
() tries to
allocate first. I.e., if the driver wants to allocate interrupts in the
following way:
5 MSI-X 1 MSI (if MSI-X allocation failed) INTx (if MSI allocation failed either)
pci_intr_alloc
() in the following
way:
int counts[PCI_INTR_TYPE_SIZE]; counts[PCI_INTR_TYPE_MSIX] = 5; counts[PCI_INTR_TYPE_MSI] = 1; counts[PCI_INTR_TYPE_INTX] = 1; error = pci_intr_alloc(pa, ihps, counts, PCI_INTR_TYPE_MSIX);
hardware max number MSI-X 1 MSI (if MSI-X allocation failed)
pci_intr_alloc
() in the following way:
int counts[PCI_INTR_TYPE_SIZE]; counts[PCI_INTR_TYPE_MSIX] = -1; /* -1 means max */ counts[PCI_INTR_TYPE_MSI] = 1; counts[PCI_INTR_TYPE_INTX] = 0; /* 0 means not use */ error = pci_intr_alloc(pa, ihps, counts, PCI_INTR_TYPE_MSIX);
3 MSI INTx (if MSI allocation failed)
pci_intr_alloc
() in the following way:
int counts[PCI_INTR_TYPE_SIZE]; counts[PCI_INTR_TYPE_MSIX] = 0; /* 0 means not use */ counts[PCI_INTR_TYPE_MSI] = 3; counts[PCI_INTR_TYPE_INTX] = 1; error = pci_intr_alloc(pa, ihps, counts, PCI_INTR_TYPE_MSI);
1 MSI-X 1 MSI INTx (if MSI/MSI-X allocation failed)
pci_intr_alloc
() in the following way:
error = pci_intr_alloc(pa, ihps, NULL, 0);
pci_intr_alloc
() returns zero on any allocation
function success, and non-zero on all allocation function failures. On
success, counts is overwritten by a really allocated
count. I.e., if 5 MSI-X is allocated, counts is
counts[PCI_INTR_TYPE_MSIX] == 5 counts[PCI_INTR_TYPE_MSI] == 0 counts[PCI_INTR_TYPE_INTX] == 0
pci_intr_type
() returns the interrupt type
of ih. The return value is
PCI_INTR_TYPE_MSIX
for MSI-X,
PCI_INTR_TYPE_MSI
for MSI, and
PCI_INTR_TYPE_INTX
for others.
pci_msi
support first appeared in
NetBSD 8.0. Support is present on
i386, amd64 and aarch64
architectures.
pci_msi
interfaces were designed and implemented by
Kengo Nakahara
<knakahara@NetBSD.org>.
January 12, 2021 | NetBSD 9.2 |