What is PRD?(Physical Region Descriptor)

C

chanakya

Guest
hi
i am a software trainee engineer who is learning the basics about writing device drivers. during this process i have encountered a problem and i m not able to understand the concept of PRD. so any help in this respect is appreciated.
 
OP
V

vikrant

Guest
Physical Region Descriptor

The physical memory region to be transferred is described by a Physical Region Descriptor (PRD). The
data transfer will proceed until all regions described by the PRDs in the table have been transferred.
Each Physical Region Descriptor entry is 8 bytes in length. The first 4 bytes specify the byte address of a
physical memory region. The next two bytes specify the count of the region in bytes (64K byte limit per
region). A value of zero in these two bytes indicates 64K. Bit 7 of the last byte indicates the end of the
table; bus master operation terminates when the last descriptor has been retired. :)
byte 3 byte 2 byte 1 byte 0
Memory Region Physical Base Address [31:1] Dword 0
Dword 1 EOT reserved Byte Count [15:1]
Memory Region 0
0

chanakya said:
hi
i am a software trainee engineer who is learning the basics about writing device drivers. during this process i have encountered a problem and i m not able to understand the concept of PRD. so any help in this respect is appreciated.
 

Shop Amazon


Shop for your Apple, Mac, iPhone and other computer products on Amazon.
We are a participant in the Amazon Services LLC Associates Program, an affiliate program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.
Top