downstream pci walk
Hello I'm writing a custom PCI driver for a hobby endpoint. Due to some "special", possibly unique, circumstance, I need to determine if two devices form a pair. As I'm using a PCI switch to connect these two devices, I'm thinking on the possibility of checking if the two devices share a common pci-pci bridge (or finding the least common ancestor in a directed graph). Basically, I'm trying to implement pci/bus.c::pci_walk_bus(), only, in a downstream direction (from end point to bridge). I could use pci_bus_upstream_bridge() to do my reverse walk but I noticed it uses a semaphore pci_bus_sem that is only made available via internal "pci.h" e.g. not available to outside modules. Along with my study, I would like to ask for advice and a push in the right direction on how can I achieve a reverse PCI walk - if that is possible. Thank you in advance for your help. ~amerei
On Thu, 17 Jul 2014 05:58:03 +0800, Amerei Acuna said:
I'm writing a custom PCI driver for a hobby endpoint. Due to some "special", possibly unique, circumstance, I need to determine if two devices form a pair. As I'm using a PCI switch to connect these two devices, I'm thinking on the possibility of checking if the two devices share a common pci-pci bridge (or finding the least common ancestor in a directed graph).
What happens if your two devices and a totally unrelated PCI device are all three downstream of the same PCI bridge?
Hi, Thank you for taking interest. I see no chance of that happening as I'm only two down stream ports of my pci switch. Upstream, I only use one port to connect the host pci bridge. Internally, it divides into multiple bridges. I'm thinking of walking downstream only _up_to_ the entry pci bridge of the switch and not any further. Please see chart for clearer explanation of topology I'm working on. http://www.electronicproducts.com/images2/FAJH_PLX_3_Nov2008.gif ~amerei On Thu, Jul 17, 2014 at 12:47 PM, <Valdis.Kletnieks@vt.edu> wrote:
On Thu, 17 Jul 2014 05:58:03 +0800, Amerei Acuna said:
I'm writing a custom PCI driver for a hobby endpoint. Due to some "special", possibly unique, circumstance, I need to determine if two devices form a pair. As I'm using a PCI switch to connect these two devices, I'm thinking on the possibility of checking if the two devices share a common pci-pci bridge (or finding the least common ancestor in a directed graph).
What happens if your two devices and a totally unrelated PCI device are all three downstream of the same PCI bridge?
sorry typo. TAKE 2! Hi, Thank you for taking interest. I see no chance of that happening as I'm only _using_ two down stream ports of my pci switch. Upstream, I only use one port to connect the host pci bridge. Internally, it divides into multiple bridges. I'm thinking of walking upstream only _up_to_ the entry pci bridge of the switch and not any further. On Thu, Jul 17, 2014 at 2:37 PM, Amerei Acuna <amerei@gmail.com> wrote:
Hi,
Thank you for taking interest. I see no chance of that happening as I'm only two down stream ports of my pci switch. Upstream, I only use one port to connect the host pci bridge. Internally, it divides into multiple bridges. I'm thinking of walking downstream only _up_to_ the entry pci bridge of the switch and not any further.
Please see chart for clearer explanation of topology I'm working on.
http://www.electronicproducts.com/images2/FAJH_PLX_3_Nov2008.gif
~amerei
On Thu, Jul 17, 2014 at 12:47 PM, <Valdis.Kletnieks@vt.edu> wrote:
On Thu, 17 Jul 2014 05:58:03 +0800, Amerei Acuna said:
I'm writing a custom PCI driver for a hobby endpoint. Due to some "special", possibly unique, circumstance, I need to determine if two devices form a pair. As I'm using a PCI switch to connect these two devices, I'm thinking on the possibility of checking if the two devices share a common pci-pci bridge (or finding the least common ancestor in a directed graph).
What happens if your two devices and a totally unrelated PCI device are all three downstream of the same PCI bridge?
participants (2)
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Amerei Acuna -
Valdis.Kletnieks＠vt.edu