Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux

connector: clean up grammar/style in documentation

The grammar in most of this file is slightly off, and some sections are
hard to read due to lack of visual clues breaking up related material.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

authored by

Mike Frysinger and committed by
David S. Miller
41144ca3 0741241c

+61 -58
+61 -58
Documentation/connector/connector.txt
··· 5 5 Kernel connector - new netlink based userspace <-> kernel space easy 6 6 to use communication module. 7 7 8 - Connector driver adds possibility to connect various agents using 9 - netlink based network. One must register callback and 10 - identifier. When driver receives special netlink message with 11 - appropriate identifier, appropriate callback will be called. 8 + The Connector driver makes it easy to connect various agents using a 9 + netlink based network. One must register a callback and an identifier. 10 + When the driver receives a special netlink message with the appropriate 11 + identifier, the appropriate callback will be called. 12 12 13 13 From the userspace point of view it's quite straightforward: 14 14 ··· 17 17 send(); 18 18 recv(); 19 19 20 - But if kernelspace want to use full power of such connections, driver 21 - writer must create special sockets, must know about struct sk_buff 22 - handling... Connector allows any kernelspace agents to use netlink 23 - based networking for inter-process communication in a significantly 20 + But if kernelspace wants to use the full power of such connections, the 21 + driver writer must create special sockets, must know about struct sk_buff 22 + handling, etc... The Connector driver allows any kernelspace agents to use 23 + netlink based networking for inter-process communication in a significantly 24 24 easier way: 25 25 26 26 int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *)); ··· 32 32 __u32 val; 33 33 }; 34 34 35 - idx and val are unique identifiers which must be registered in 36 - connector.h for in-kernel usage. void (*callback) (void *) - is a 37 - callback function which will be called when message with above idx.val 38 - will be received by connector core. Argument for that function must 35 + idx and val are unique identifiers which must be registered in the 36 + connector.h header for in-kernel usage. void (*callback) (void *) is a 37 + callback function which will be called when a message with above idx.val 38 + is received by the connector core. The argument for that function must 39 39 be dereferenced to struct cn_msg *. 40 40 41 41 struct cn_msg 42 42 { 43 - struct cb_id id; 43 + struct cb_id id; 44 44 45 45 __u32 seq; 46 46 __u32 ack; ··· 55 55 56 56 int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *)); 57 57 58 - Registers new callback with connector core. 58 + Registers new callback with connector core. 59 59 60 - struct cb_id *id - unique connector's user identifier. 61 - It must be registered in connector.h for legal in-kernel users. 62 - char *name - connector's callback symbolic name. 63 - void (*callback) (void *) - connector's callback. 60 + struct cb_id *id - unique connector's user identifier. 61 + It must be registered in connector.h for legal in-kernel users. 62 + char *name - connector's callback symbolic name. 63 + void (*callback) (void *) - connector's callback. 64 64 Argument must be dereferenced to struct cn_msg *. 65 + 65 66 66 67 void cn_del_callback(struct cb_id *id); 67 68 68 - Unregisters new callback with connector core. 69 + Unregisters new callback with connector core. 69 70 70 - struct cb_id *id - unique connector's user identifier. 71 + struct cb_id *id - unique connector's user identifier. 72 + 71 73 72 74 int cn_netlink_send(struct cn_msg *msg, u32 __groups, int gfp_mask); 73 75 74 - Sends message to the specified groups. It can be safely called from 75 - softirq context, but may silently fail under strong memory pressure. 76 - If there are no listeners for given group -ESRCH can be returned. 76 + Sends message to the specified groups. It can be safely called from 77 + softirq context, but may silently fail under strong memory pressure. 78 + If there are no listeners for given group -ESRCH can be returned. 77 79 78 - struct cn_msg * - message header(with attached data). 79 - u32 __group - destination group. 80 + struct cn_msg * - message header(with attached data). 81 + u32 __group - destination group. 80 82 If __group is zero, then appropriate group will 81 83 be searched through all registered connector users, 82 84 and message will be delivered to the group which was 83 85 created for user with the same ID as in msg. 84 86 If __group is not zero, then message will be delivered 85 87 to the specified group. 86 - int gfp_mask - GFP mask. 88 + int gfp_mask - GFP mask. 87 89 88 - Note: When registering new callback user, connector core assigns 89 - netlink group to the user which is equal to it's id.idx. 90 + Note: When registering new callback user, connector core assigns 91 + netlink group to the user which is equal to it's id.idx. 90 92 91 93 /*****************************************/ 92 94 Protocol description. 93 95 /*****************************************/ 94 96 95 - Current offers transport layer with fixed header. Recommended 96 - protocol which uses such header is following: 97 + The current framework offers a transport layer with fixed headers. The 98 + recommended protocol which uses such a header is as following: 97 99 98 100 msg->seq and msg->ack are used to determine message genealogy. When 99 - someone sends message it puts there locally unique sequence and random 100 - acknowledge numbers. Sequence number may be copied into 101 + someone sends a message, they use a locally unique sequence and random 102 + acknowledge number. The sequence number may be copied into 101 103 nlmsghdr->nlmsg_seq too. 102 104 103 - Sequence number is incremented with each message to be sent. 105 + The sequence number is incremented with each message sent. 104 106 105 - If we expect reply to our message, then sequence number in received 106 - message MUST be the same as in original message, and acknowledge 107 - number MUST be the same + 1. 107 + If you expect a reply to the message, then the sequence number in the 108 + received message MUST be the same as in the original message, and the 109 + acknowledge number MUST be the same + 1. 108 110 109 - If we receive message and it's sequence number is not equal to one we 110 - are expecting, then it is new message. If we receive message and it's 111 - sequence number is the same as one we are expecting, but it's 112 - acknowledge is not equal acknowledge number in original message + 1, 113 - then it is new message. 111 + If we receive a message and its sequence number is not equal to one we 112 + are expecting, then it is a new message. If we receive a message and 113 + its sequence number is the same as one we are expecting, but its 114 + acknowledge is not equal to the acknowledge number in the original 115 + message + 1, then it is a new message. 114 116 115 - Obviously, protocol header contains above id. 117 + Obviously, the protocol header contains the above id. 116 118 117 - connector allows event notification in the following form: kernel 119 + The connector allows event notification in the following form: kernel 118 120 driver or userspace process can ask connector to notify it when 119 - selected id's will be turned on or off(registered or unregistered it's 120 - callback). It is done by sending special command to connector 121 - driver(it also registers itself with id={-1, -1}). 121 + selected ids will be turned on or off (registered or unregistered its 122 + callback). It is done by sending a special command to the connector 123 + driver (it also registers itself with id={-1, -1}). 122 124 123 - As example of usage Documentation/connector now contains cn_test.c - 124 - testing module which uses connector to request notification and to 125 - send messages. 125 + As example of this usage can be found in the cn_test.c module which 126 + uses the connector to request notification and to send messages. 126 127 127 128 /*****************************************/ 128 129 Reliability. 129 130 /*****************************************/ 130 131 131 - Netlink itself is not reliable protocol, that means that messages can 132 + Netlink itself is not a reliable protocol. That means that messages can 132 133 be lost due to memory pressure or process' receiving queue overflowed, 133 - so caller is warned must be prepared. That is why struct cn_msg [main 134 - connector's message header] contains u32 seq and u32 ack fields. 134 + so caller is warned that it must be prepared. That is why the struct 135 + cn_msg [main connector's message header] contains u32 seq and u32 ack 136 + fields. 135 137 136 138 /*****************************************/ 137 139 Userspace usage. 138 140 /*****************************************/ 141 + 139 142 2.6.14 has a new netlink socket implementation, which by default does not 140 - allow to send data to netlink groups other than 1. 141 - So, if to use netlink socket (for example using connector) 142 - with different group number userspace application must subscribe to 143 - that group. It can be achieved by following pseudocode: 143 + allow people to send data to netlink groups other than 1. 144 + So, if you wish to use a netlink socket (for example using connector) 145 + with a different group number, the userspace application must subscribe to 146 + that group first. It can be achieved by the following pseudocode: 144 147 145 148 s = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR); 146 149 ··· 163 160 } 164 161 165 162 Where 270 above is SOL_NETLINK, and 1 is a NETLINK_ADD_MEMBERSHIP socket 166 - option. To drop multicast subscription one should call above socket option 167 - with NETLINK_DROP_MEMBERSHIP parameter which is defined as 0. 163 + option. To drop a multicast subscription, one should call the above socket 164 + option with the NETLINK_DROP_MEMBERSHIP parameter which is defined as 0. 168 165 169 166 2.6.14 netlink code only allows to select a group which is less or equal to 170 167 the maximum group number, which is used at netlink_kernel_create() time.