diff options
Diffstat (limited to 'share/man/man9/uio.9')
| -rw-r--r-- | share/man/man9/uio.9 | 45 |
1 files changed, 38 insertions, 7 deletions
diff --git a/share/man/man9/uio.9 b/share/man/man9/uio.9 index fb27c9c..9d569b7 100644 --- a/share/man/man9/uio.9 +++ b/share/man/man9/uio.9 @@ -25,12 +25,13 @@ .\" .\" $FreeBSD$ .\" -.Dd March 21, 2010 +.Dd July 9, 2011 .Dt UIO 9 .Os .Sh NAME .Nm uio , -.Nm uiomove +.Nm uiomove , +.Nm uiomove_nofault .Nd device driver I/O routines .Sh SYNOPSIS .In sys/types.h @@ -48,11 +49,15 @@ struct uio { .Ed .Ft int .Fn uiomove "void *buf" "int howmuch" "struct uio *uiop" +.Ft int +.Fn uiomove_nofault "void *buf" "int howmuch" "struct uio *uiop" .Sh DESCRIPTION -The function +The functions .Fn uiomove -is used to handle transfer of data between buffers and I/O vectors -that might possibly also cross the user/kernel space boundary. +and +.Fn uiomove_nofault +are used to transfer data between buffers and I/O vectors that might +possibly cross the user/kernel space boundary. .Pp As a result of any .Xr read 2 , @@ -71,6 +76,8 @@ being passed. The transfer request is encoded in this structure. The driver itself should use .Fn uiomove +or +.Fn uiomove_nofault to get at the data in this structure. .Pp The fields in the @@ -99,7 +106,7 @@ Do not copy, already in object. .El .It Va uio_rw The direction of the desired transfer, either -.Dv UIO_READ , +.Dv UIO_READ or .Dv UIO_WRITE . .It Va uio_td @@ -110,10 +117,24 @@ for the associated thread; used if indicates that the transfer is to be made from/to a process's address space. .El +.Pp +The function +.Fn uiomove_nofault +requires that the buffer and I/O vectors be accessible without +incurring a page fault. +The source and destination addresses must be physically mapped for +read and write access, respectively, and neither the source nor +destination addresses may be pageable. +Thus, the function +.Fn uiomove_nofault +can be called from contexts where acquiring virtual memory system +locks or sleeping are prohibited. .Sh RETURN VALUES On success .Fn uiomove -will return 0, on error it will return an appropriate errno. +and +.Fn uiomove_nofault +will return 0; on error they will return an appropriate error code. .Sh EXAMPLES The idea is that the driver maintains a private buffer for its data, and processes the request in chunks of maximal the size of this @@ -156,6 +177,8 @@ fooread(dev_t dev, struct uio *uio, int flag) .Ed .Sh ERRORS .Fn uiomove +and +.Fn uiomove_nofault will fail and return the following error code if: .Bl -tag -width Er .It Bq Er EFAULT @@ -166,6 +189,14 @@ or returned .Er EFAULT .El +.Pp +In addition, +.Fn uiomove_nofault +will fail and return the following error code if: +.Bl -tag -width Er +.It Bq Er EFAULT +A page fault occurs. +.El .Sh SEE ALSO .Xr read 2 , .Xr readv 2 , |
