diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/DMA-API.txt | 49 | ||||
| -rw-r--r-- | Documentation/DMA-mapping.txt | 22 | ||||
| -rw-r--r-- | Documentation/i2c/busses/i2c-parport | 16 | ||||
| -rw-r--r-- | Documentation/networking/xfrm_sync.txt | 166 | ||||
| -rw-r--r-- | Documentation/serial/driver | 22 |
5 files changed, 247 insertions, 28 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 1af0f2d..2ffb0d6 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -33,7 +33,9 @@ pci_alloc_consistent(struct pci_dev *dev, size_t size, Consistent memory is memory for which a write by either the device or the processor can immediately be read by the processor or device -without having to worry about caching effects. +without having to worry about caching effects. (You may however need +to make sure to flush the processor's write buffers before telling +devices to read that memory.) This routine allocates a region of <size> bytes of consistent memory. it also returns a <dma_handle> which may be cast to an unsigned @@ -304,12 +306,12 @@ dma address with dma_mapping_error(). A non zero return value means the mapping could not be created and the driver should take appropriate action (eg reduce current DMA mapping usage or delay and try again later). -int -dma_map_sg(struct device *dev, struct scatterlist *sg, int nents, - enum dma_data_direction direction) -int -pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg, - int nents, int direction) + int + dma_map_sg(struct device *dev, struct scatterlist *sg, + int nents, enum dma_data_direction direction) + int + pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg, + int nents, int direction) Maps a scatter gather list from the block layer. @@ -327,12 +329,33 @@ critical that the driver do something, in the case of a block driver aborting the request or even oopsing is better than doing nothing and corrupting the filesystem. -void -dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nhwentries, - enum dma_data_direction direction) -void -pci_unmap_sg(struct pci_dev *hwdev, struct scatterlist *sg, - int nents, int direction) +With scatterlists, you use the resulting mapping like this: + + int i, count = dma_map_sg(dev, sglist, nents, direction); + struct scatterlist *sg; + + for (i = 0, sg = sglist; i < count; i++, sg++) { + hw_address[i] = sg_dma_address(sg); + hw_len[i] = sg_dma_len(sg); + } + +where nents is the number of entries in the sglist. + +The implementation is free to merge several consecutive sglist entries +into one (e.g. with an IOMMU, or if several pages just happen to be +physically contiguous) and returns the actual number of sg entries it +mapped them to. On failure 0, is returned. + +Then you should loop count times (note: this can be less than nents times) +and use sg_dma_address() and sg_dma_len() macros where you previously +accessed sg->address and sg->length as shown above. + + void + dma_unmap_sg(struct device *dev, struct scatterlist *sg, + int nhwentries, enum dma_data_direction direction) + void + pci_unmap_sg(struct pci_dev *hwdev, struct scatterlist *sg, + int nents, int direction) unmap the previously mapped scatter/gather list. All the parameters must be the same as those and passed in to the scatter/gather mapping diff --git a/Documentation/DMA-mapping.txt b/Documentation/DMA-mapping.txt index 10bf4de..7c717699 100644 --- a/Documentation/DMA-mapping.txt +++ b/Documentation/DMA-mapping.txt @@ -58,11 +58,15 @@ translating each of those pages back to a kernel address using something like __va(). [ EDIT: Update this when we integrate Gerd Knorr's generic code which does this. ] -This rule also means that you may not use kernel image addresses -(ie. items in the kernel's data/text/bss segment, or your driver's) -nor may you use kernel stack addresses for DMA. Both of these items -might be mapped somewhere entirely different than the rest of physical -memory. +This rule also means that you may use neither kernel image addresses +(items in data/text/bss segments), nor module image addresses, nor +stack addresses for DMA. These could all be mapped somewhere entirely +different than the rest of physical memory. Even if those classes of +memory could physically work with DMA, you'd need to ensure the I/O +buffers were cacheline-aligned. Without that, you'd see cacheline +sharing problems (data corruption) on CPUs with DMA-incoherent caches. +(The CPU could write to one word, DMA would write to a different one +in the same cache line, and one of them could be overwritten.) Also, this means that you cannot take the return of a kmap() call and DMA to/from that. This is similar to vmalloc(). @@ -284,6 +288,11 @@ There are two types of DMA mappings: in order to get correct behavior on all platforms. + Also, on some platforms your driver may need to flush CPU write + buffers in much the same way as it needs to flush write buffers + found in PCI bridges (such as by reading a register's value + after writing it). + - Streaming DMA mappings which are usually mapped for one DMA transfer, unmapped right after it (unless you use pci_dma_sync_* below) and for which hardware can optimize for sequential accesses. @@ -303,6 +312,9 @@ There are two types of DMA mappings: Neither type of DMA mapping has alignment restrictions that come from PCI, although some devices may have such restrictions. +Also, systems with caches that aren't DMA-coherent will work better +when the underlying buffers don't share cache lines with other data. + Using Consistent DMA mappings. diff --git a/Documentation/i2c/busses/i2c-parport b/Documentation/i2c/busses/i2c-parport index d9f23c0..77b995d 100644 --- a/Documentation/i2c/busses/i2c-parport +++ b/Documentation/i2c/busses/i2c-parport @@ -12,18 +12,22 @@ meant as a replacement for the older, individual drivers: teletext adapters) It currently supports the following devices: - * Philips adapter - * home brew teletext adapter - * Velleman K8000 adapter - * ELV adapter - * Analog Devices evaluation boards (ADM1025, ADM1030, ADM1031, ADM1032) - * Barco LPT->DVI (K5800236) adapter + * (type=0) Philips adapter + * (type=1) home brew teletext adapter + * (type=2) Velleman K8000 adapter + * (type=3) ELV adapter + * (type=4) Analog Devices ADM1032 evaluation board + * (type=5) Analog Devices evaluation boards: ADM1025, ADM1030, ADM1031 + * (type=6) Barco LPT->DVI (K5800236) adapter These devices use different pinout configurations, so you have to tell the driver what you have, using the type module parameter. There is no way to autodetect the devices. Support for different pinout configurations can be easily added when needed. +Earlier kernels defaulted to type=0 (Philips). But now, if the type +parameter is missing, the driver will simply fail to initialize. + Building your own adapter ------------------------- diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt new file mode 100644 index 0000000..8be626f --- /dev/null +++ b/Documentation/networking/xfrm_sync.txt @@ -0,0 +1,166 @@ + +The sync patches work is based on initial patches from +Krisztian <hidden@balabit.hu> and others and additional patches +from Jamal <hadi@cyberus.ca>. + +The end goal for syncing is to be able to insert attributes + generate +events so that the an SA can be safely moved from one machine to another +for HA purposes. +The idea is to synchronize the SA so that the takeover machine can do +the processing of the SA as accurate as possible if it has access to it. + +We already have the ability to generate SA add/del/upd events. +These patches add ability to sync and have accurate lifetime byte (to +ensure proper decay of SAs) and replay counters to avoid replay attacks +with as minimal loss at failover time. +This way a backup stays as closely uptodate as an active member. + +Because the above items change for every packet the SA receives, +it is possible for a lot of the events to be generated. +For this reason, we also add a nagle-like algorithm to restrict +the events. i.e we are going to set thresholds to say "let me +know if the replay sequence threshold is reached or 10 secs have passed" +These thresholds are set system-wide via sysctls or can be updated +per SA. + +The identified items that need to be synchronized are: +- the lifetime byte counter +note that: lifetime time limit is not important if you assume the failover +machine is known ahead of time since the decay of the time countdown +is not driven by packet arrival. +- the replay sequence for both inbound and outbound + +1) Message Structure +---------------------- + +nlmsghdr:aevent_id:optional-TLVs. + +The netlink message types are: + +XFRM_MSG_NEWAE and XFRM_MSG_GETAE. + +A XFRM_MSG_GETAE does not have TLVs. +A XFRM_MSG_NEWAE will have at least two TLVs (as is +discussed further below). + +aevent_id structure looks like: + + struct xfrm_aevent_id { + struct xfrm_usersa_id sa_id; + __u32 flags; + }; + +xfrm_usersa_id in this message layout identifies the SA. + +flags are used to indicate different things. The possible +flags are: + XFRM_AE_RTHR=1, /* replay threshold*/ + XFRM_AE_RVAL=2, /* replay value */ + XFRM_AE_LVAL=4, /* lifetime value */ + XFRM_AE_ETHR=8, /* expiry timer threshold */ + XFRM_AE_CR=16, /* Event cause is replay update */ + XFRM_AE_CE=32, /* Event cause is timer expiry */ + XFRM_AE_CU=64, /* Event cause is policy update */ + +How these flags are used is dependent on the direction of the +message (kernel<->user) as well the cause (config, query or event). +This is described below in the different messages. + +The pid will be set appropriately in netlink to recognize direction +(0 to the kernel and pid = processid that created the event +when going from kernel to user space) + +A program needs to subscribe to multicast group XFRMNLGRP_AEVENTS +to get notified of these events. + +2) TLVS reflect the different parameters: +----------------------------------------- + +a) byte value (XFRMA_LTIME_VAL) +This TLV carries the running/current counter for byte lifetime since +last event. + +b)replay value (XFRMA_REPLAY_VAL) +This TLV carries the running/current counter for replay sequence since +last event. + +c)replay threshold (XFRMA_REPLAY_THRESH) +This TLV carries the threshold being used by the kernel to trigger events +when the replay sequence is exceeded. + +d) expiry timer (XFRMA_ETIMER_THRESH) +This is a timer value in milliseconds which is used as the nagle +value to rate limit the events. + +3) Default configurations for the parameters: +---------------------------------------------- + +By default these events should be turned off unless there is +at least one listener registered to listen to the multicast +group XFRMNLGRP_AEVENTS. + +Programs installing SAs will need to specify the two thresholds, however, +in order to not change existing applications such as racoon +we also provide default threshold values for these different parameters +in case they are not specified. + +the two sysctls/proc entries are: +a) /proc/sys/net/core/sysctl_xfrm_aevent_etime +used to provide default values for the XFRMA_ETIMER_THRESH in incremental +units of time of 100ms. The default is 10 (1 second) + +b) /proc/sys/net/core/sysctl_xfrm_aevent_rseqth +used to provide default values for XFRMA_REPLAY_THRESH parameter +in incremental packet count. The default is two packets. + +4) Message types +---------------- + +a) XFRM_MSG_GETAE issued by user-->kernel. +XFRM_MSG_GETAE does not carry any TLVs. +The response is a XFRM_MSG_NEWAE which is formatted based on what +XFRM_MSG_GETAE queried for. +The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. +*if XFRM_AE_RTHR flag is set, then XFRMA_REPLAY_THRESH is also retrieved +*if XFRM_AE_ETHR flag is set, then XFRMA_ETIMER_THRESH is also retrieved + +b) XFRM_MSG_NEWAE is issued by either user space to configure +or kernel to announce events or respond to a XFRM_MSG_GETAE. + +i) user --> kernel to configure a specific SA. +any of the values or threshold parameters can be updated by passing the +appropriate TLV. +A response is issued back to the sender in user space to indicate success +or failure. +In the case of success, additionally an event with +XFRM_MSG_NEWAE is also issued to any listeners as described in iii). + +ii) kernel->user direction as a response to XFRM_MSG_GETAE +The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. +The threshold TLVs will be included if explicitly requested in +the XFRM_MSG_GETAE message. + +iii) kernel->user to report as event if someone sets any values or +thresholds for an SA using XFRM_MSG_NEWAE (as described in #i above). +In such a case XFRM_AE_CU flag is set to inform the user that +the change happened as a result of an update. +The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. + +iv) kernel->user to report event when replay threshold or a timeout +is exceeded. +In such a case either XFRM_AE_CR (replay exceeded) or XFRM_AE_CE (timeout +happened) is set to inform the user what happened. +Note the two flags are mutually exclusive. +The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. + +Exceptions to threshold settings +-------------------------------- + +If you have an SA that is getting hit by traffic in bursts such that +there is a period where the timer threshold expires with no packets +seen, then an odd behavior is seen as follows: +The first packet arrival after a timer expiry will trigger a timeout +aevent; i.e we dont wait for a timeout period or a packet threshold +to be reached. This is done for simplicity and efficiency reasons. + +-JHS diff --git a/Documentation/serial/driver b/Documentation/serial/driver index 42ef997..df82116 100644 --- a/Documentation/serial/driver +++ b/Documentation/serial/driver @@ -3,14 +3,11 @@ -------------------- - $Id: driver,v 1.10 2002/07/22 15:27:30 rmk Exp $ - - This document is meant as a brief overview of some aspects of the new serial driver. It is not complete, any questions you have should be directed to <rmk@arm.linux.org.uk> -The reference implementation is contained within serial_amba.c. +The reference implementation is contained within amba_pl011.c. @@ -31,6 +28,11 @@ The serial core provides a few helper functions. This includes identifing the correct port structure (via uart_get_console) and decoding command line arguments (uart_parse_options). +There is also a helper function (uart_write_console) which performs a +character by character write, translating newlines to CRLF sequences. +Driver writers are recommended to use this function rather than implementing +their own version. + Locking ------- @@ -86,6 +88,7 @@ hardware. - TIOCM_DTR DTR signal. - TIOCM_OUT1 OUT1 signal. - TIOCM_OUT2 OUT2 signal. + - TIOCM_LOOP Set the port into loopback mode. If the appropriate bit is set, the signal should be driven active. If the bit is clear, the signal should be driven inactive. @@ -141,6 +144,10 @@ hardware. enable_ms(port) Enable the modem status interrupts. + This method may be called multiple times. Modem status + interrupts should be disabled when the shutdown method is + called. + Locking: port->lock taken. Interrupts: locally disabled. This call must not sleep @@ -160,6 +167,8 @@ hardware. state. Enable the port for reception. It should not activate RTS nor DTR; this will be done via a separate call to set_mctrl. + This method will only be called when the port is initially opened. + Locking: port_sem taken. Interrupts: globally disabled. @@ -169,6 +178,11 @@ hardware. RTS nor DTR; this will have already been done via a separate call to set_mctrl. + Drivers must not access port->info once this call has completed. + + This method will only be called when there are no more users of + this port. + Locking: port_sem taken. Interrupts: caller dependent. |