For a PCI device to request memory resource of ,say 1MB, should it have onboard memory of 1MB ? TIA
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I'm guessing that you're asking if it has to have as much memory as the resource. If that's the case, the answer is no. You just have to respond to any request in that region.
In other words, you could request a 1 GB region and only respond with useful data in the first 1 MB (respond to any other read with zeros), or map the 1 MB 1024 times into the 1 GB, or anything else you decide.
Sorry if I totally missed the intent of your question,
Myles
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From: linuxbios-bounces@linuxbios.org [mailto:linuxbios-bounces@linuxbios.org] On Behalf Of Baski Sent: Wednesday, January 09, 2008 7:06 PM To: linuxbios@linuxbios.org Subject: [LinuxBIOS] PCI device memory resource
For a PCI device to request memory resource of ,say 1MB, should it have onboard memory of 1MB ? TIA
-- People wielding power and authority always desire to destroy the sources which gave them that power. Or, is it the other way round?
_____
Never miss a thing. Make Yahoo http://us.rd.yahoo.com/evt=51438/*http:/www.yahoo.com/r/hs your homepage.
Pardon my bad phrasing of the original question. I have a mem-mapped PCI controller which has no on-board memory, but is asking for 32MB memory resource. Is this legal? While BIOS gives it 32MB address space, who is going to malloc and give it the required memory to work with? Thanks - Baski Myles Watson myles@pel.cs.byu.edu wrote: v:* {behavior:url(#default#VML);} o:* {behavior:url(#default#VML);} w:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Im guessing that youre asking if it has to have as much memory as the resource. If thats the case, the answer is no. You just have to respond to any request in that region.
In other words, you could request a 1 GB region and only respond with useful data in the first 1 MB (respond to any other read with zeros), or map the 1 MB 1024 times into the 1 GB, or anything else you decide.
Sorry if I totally missed the intent of your question, Myles
---------------------------------
From: linuxbios-bounces@linuxbios.org [mailto:linuxbios-bounces@linuxbios.org] On Behalf Of Baski Sent: Wednesday, January 09, 2008 7:06 PM To: linuxbios@linuxbios.org Subject: [LinuxBIOS] PCI device memory resource
For a PCI device to request memory resource of ,say 1MB, should it have onboard memory of 1MB ? TIA
-- People wielding power and authority always desire to destroy the sources which gave them that power. Or, is it the other way round?
---------------------------------
Never miss a thing. Make Yahoo your homepage.
-- People wielding power and authority always desire to destroy the sources which gave them that power. Or, is it the other way round?
--------------------------------- Never miss a thing. Make Yahoo your homepage.
I think the confusion comes because of the difference between memory and memory address space. The PCI controller is asking for 32 MB of the physical address space, not memory. When the BIOS allocates this region in the address space, it is trusting that the PCI controller will respond to any reads/writes to that address space.
There is no need to have actual RAM backing up every bit of address space, but the device needs to respond to accesses to its address space.
Myles
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From: Baski [mailto:kbaski@yahoo.com] Sent: Thursday, January 10, 2008 8:14 AM To: myles@mouselemur.cs.byu.edu; linuxbios@linuxbios.org Subject: RE: [LinuxBIOS] PCI device memory resource
Pardon my bad phrasing of the original question. I have a mem-mapped PCI controller which has no on-board memory, but is asking for 32MB memory resource. Is this legal? While BIOS gives it 32MB address space, who is going to malloc and give it the required memory to work with? Thanks - Baski Myles Watson myles@pel.cs.byu.edu wrote:
I'm guessing that you're asking if it has to have as much memory as the resource. If that's the case, the answer is no. You just have to respond to any request in that region.
In other words, you could request a 1 GB region and only respond with useful data in the first 1 MB (respond to any other read with zeros), or map the 1 MB 1024 times into the 1 GB, or anything else you decide.
Sorry if I totally missed the intent of your question,
Myles
_____
From: linuxbios-bounces@linuxbios.org [mailto:linuxbios-bounces@linuxbios.org] On Behalf Of Baski Sent: Wednesday, January 09, 2008 7:06 PM To: linuxbios@linuxbios.org Subject: [LinuxBIOS] PCI device memory resource
For a PCI device to request memory resource of ,say 1MB, should it have onboard memory of 1MB ? TIA
-- People wielding power and authority always desire to destroy the sources which gave them that power. Or, is it the other way round?
_____
Never miss a thing. Make Yahoo http://us.rd.yahoo.com/evt=51438/*http:/www.yahoo.com/r/hs your homepage.
-- People wielding power and authority always desire to destroy the sources which gave them that power. Or, is it the other way round?
_____
Never miss a thing. Make Yahoo http://us.rd.yahoo.com/evt=51438/*http:/www.yahoo.com/r/hs your homepage.
-
Baski -
Myles Watson