Allocating a large chunk of memory in the kernel (2mb)

[David Frascone]

I need to allocate 2mb for a brain dead driver. The existing driver likes to get it's memory by using mem=<realmem = 2mb>, then ioremaping the top of physical memory to get raw access to it.

Basically, the area is for DMA / shared memory for a pci card.

So, I'm trying to remove the mem= dependency, and just allocate a large buffer to use with the driver. But, kmalloc doesn't like to give out chunks that size.

So, how do I malloc 2Mb of contiguous space?

-Dave

[root]

?? man malloc ??

Post by David Frascone
I need to allocate 2mb for a brain dead driver. The existing driver likes to get it's memory by using mem=<realmem = 2mb>, then ioremaping the top of physical memory to get raw access to it.
Basically, the area is for DMA / shared memory for a pci card.
So, I'm trying to remove the mem= dependency, and just allocate a large buffer to use with the driver. But, kmalloc doesn't like to give out chunks that size.
So, how do I malloc 2Mb of contiguous space?
-Dave

[David Frascone]

I can only assume that this is a troll. Otherwise it would take a pretty big idiot to ignore the word "kernel" in the subject, and ignoring the sentence in the body where I said that kmalloc will not return me 2mb of memory.

Unless I'm the moron, and malloc was added to kernel space . . . let me know.

-Dave

On Sun, 02 Jan 2005 23:31:13 -0600

Post by root
?? man malloc ??

Post by David Frascone
I need to allocate 2mb for a brain dead driver. The existing driver likes to get it's memory by using mem=<realmem = 2mb>, then ioremaping the top of physical memory to get raw access to it.
Basically, the area is for DMA / shared memory for a pci card.
So, I'm trying to remove the mem= dependency, and just allocate a large buffer to use with the driver. But, kmalloc doesn't like to give out chunks that size.
So, how do I malloc 2Mb of contiguous space?
-Dave

[Mihai Osian]

Post by David Frascone
I need to allocate 2mb for a brain dead driver. The existing driver likes to get it's memory by using mem=<realmem = 2mb>, then ioremaping the top of physical memory to get raw access to it.
Basically, the area is for DMA / shared memory for a pci card.
So, I'm trying to remove the mem= dependency, and just allocate a large buffer to use with the driver. But, kmalloc doesn't like to give out chunks that size.
So, how do I malloc 2Mb of contiguous space?
-Dave

Hi Dave,

Perhaps __get_dma_pages ? Never used this function myself, but it's
described in http://www.xml.com/ldd/chapter/book/ch07.html
Anyway, linux.kernel might be a better newsgroup for you to ask.

Mihai

[David Frascone]

On Mon, 03 Jan 2005 15:58:17 +0100

Post by Mihai Osian

Post by David Frascone
I need to allocate 2mb for a brain dead driver. The existing driver likes to get it's memory by using mem=<realmem = 2mb>, then ioremaping the top of physical memory to get raw access to it.
Basically, the area is for DMA / shared memory for a pci card.
So, I'm trying to remove the mem= dependency, and just allocate a large buffer to use with the driver. But, kmalloc doesn't like to give out chunks that size.
So, how do I malloc 2Mb of contiguous space?
-Dave

Hi Dave,
Perhaps __get_dma_pages ? Never used this function myself, but it's
described in http://www.xml.com/ldd/chapter/book/ch07.html
Anyway, linux.kernel might be a better newsgroup for you to ask.

Thanks, that is exactly the direction I'm looking.

I still don't think that's going to be enough, though. Looks like it maxes out at 2mb, and I might need two 2mb chunks. I'll give it a try though. I'm leaning toward the bigphysmem patch now. It might give me what I need.

I'll post when I find a solution.

-Dave

[David Frascone]

On Mon, 03 Jan 2005 15:02:08 GMT

Post by David Frascone
On Mon, 03 Jan 2005 15:58:17 +0100

Post by Mihai Osian

Post by David Frascone
I need to allocate 2mb for a brain dead driver. The existing driver likes to get it's memory by using mem=<realmem = 2mb>, then ioremaping the top of physical memory to get raw access to it.
Basically, the area is for DMA / shared memory for a pci card.
So, I'm trying to remove the mem= dependency, and just allocate a large buffer to use with the driver. But, kmalloc doesn't like to give out chunks that size.
So, how do I malloc 2Mb of contiguous space?
-Dave

Hi Dave,
Perhaps __get_dma_pages ? Never used this function myself, but it's
described in http://www.xml.com/ldd/chapter/book/ch07.html
Anyway, linux.kernel might be a better newsgroup for you to ask.

Thanks, that is exactly the direction I'm looking.
I still don't think that's going to be enough, though. Looks like it maxes out at 2mb, and I might need two 2mb chunks. I'll give it a try though. I'm leaning toward the bigphysmem patch now. It might give me what I need.
I'll post when I find a solution.

Get DMA pages worked! It let me use an order of 9, for 512 4k pages (2mb). And, I was able to allocate both that I needed.

Thanks so much for your help!

-Dave