[PATCH] ipmi: si start transaction hook

Some commands, on some system BMCs, don't respond at at all.  This is seen on
Dell PowerEdge x6xx and x7xx systems with IPMI 1.0 BT controllers when a "Get
SDR" command is issued, with a length field of 0x3A, which happens to be the
length of about SDR entries.  If another length is passed, this command
succeeds.

This patch adds general infrastructure for receiving commands before they're
passed down to the low-level drivers, such that they can be completed
immediately, or modified, prior to being sent to ->start_transaction().

Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/char/ipmi/ipmi_si_intf.c

@@ -51,6 +51,7 @@
 #include <linux/list.h>
 #include <linux/pci.h>
 #include <linux/ioport.h>
+#include <linux/notifier.h>
 #include <asm/irq.h>
 #ifdef CONFIG_HIGH_RES_TIMERS
 #include <linux/hrtime.h>
@@ -222,6 +223,12 @@ struct smi_info
 	unsigned long incoming_messages;
 };
 
+static struct notifier_block *xaction_notifier_list;
+static int register_xaction_notifier(struct notifier_block * nb)
+{
+	return notifier_chain_register(&xaction_notifier_list, nb);
+}
+
 static void si_restart_short_timer(struct smi_info *smi_info);
 
 static void deliver_recv_msg(struct smi_info *smi_info,
@@ -281,6 +288,11 @@ static enum si_sm_result start_next_msg(struct smi_info *smi_info)
 		do_gettimeofday(&t);
 		printk("**Start2: %d.%9.9d\n", t.tv_sec, t.tv_usec);
 #endif
+		err = notifier_call_chain(&xaction_notifier_list, 0, smi_info);
+		if (err & NOTIFY_STOP_MASK) {
+			rv = SI_SM_CALL_WITHOUT_DELAY;
+			goto out;
+		}
 		err = smi_info->handlers->start_transaction(
 			smi_info->si_sm,
 			smi_info->curr_msg->data,
@@ -291,6 +303,7 @@ static enum si_sm_result start_next_msg(struct smi_info *smi_info)
 
 		rv = SI_SM_CALL_WITHOUT_DELAY;
 	}
+	out:
 	spin_unlock(&(smi_info->msg_lock));
 
 	return rv;
@@ -2080,6 +2093,71 @@ static void setup_dell_poweredge_oem_data_handler(struct smi_info *smi_info)
 	}
 }
 
+#define CANNOT_RETURN_REQUESTED_LENGTH 0xCA
+static void return_hosed_msg_badsize(struct smi_info *smi_info)
+{
+	struct ipmi_smi_msg *msg = smi_info->curr_msg;
+
+	/* Make it a reponse */
+	msg->rsp[0] = msg->data[0] | 4;
+	msg->rsp[1] = msg->data[1];
+	msg->rsp[2] = CANNOT_RETURN_REQUESTED_LENGTH;
+	msg->rsp_size = 3;
+	smi_info->curr_msg = NULL;
+	deliver_recv_msg(smi_info, msg);
+}
+
+/*
+ * dell_poweredge_bt_xaction_handler
+ * @info - smi_info.device_id must be populated
+ *
+ * Dell PowerEdge servers with the BT interface (x6xx and 1750) will
+ * not respond to a Get SDR command if the length of the data
+ * requested is exactly 0x3A, which leads to command timeouts and no
+ * data returned.  This intercepts such commands, and causes userspace
+ * callers to try again with a different-sized buffer, which succeeds.
+ */
+
+#define STORAGE_NETFN 0x0A
+#define STORAGE_CMD_GET_SDR 0x23
+static int dell_poweredge_bt_xaction_handler(struct notifier_block *self,
+					     unsigned long unused,
+					     void *in)
+{
+	struct smi_info *smi_info = in;
+	unsigned char *data = smi_info->curr_msg->data;
+	unsigned int size   = smi_info->curr_msg->data_size;
+	if (size >= 8 &&
+	    (data[0]>>2) == STORAGE_NETFN &&
+	    data[1] == STORAGE_CMD_GET_SDR &&
+	    data[7] == 0x3A) {
+		return_hosed_msg_badsize(smi_info);
+		return NOTIFY_STOP;
+	}
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block dell_poweredge_bt_xaction_notifier = {
+	.notifier_call	= dell_poweredge_bt_xaction_handler,
+};
+
+/*
+ * setup_dell_poweredge_bt_xaction_handler
+ * @info - smi_info.device_id must be filled in already
+ *
+ * Fills in smi_info.device_id.start_transaction_pre_hook
+ * when we know what function to use there.
+ */
+static void
+setup_dell_poweredge_bt_xaction_handler(struct smi_info *smi_info)
+{
+	struct ipmi_device_id *id = &smi_info->device_id;
+	const char mfr[3]=DELL_IANA_MFR_ID;
+ 	if (! memcmp(mfr, id->manufacturer_id, sizeof(mfr)) &&
+	    smi_info->si_type == SI_BT)
+		register_xaction_notifier(&dell_poweredge_bt_xaction_notifier);
+}
+
 /*
  * setup_oem_data_handler
  * @info - smi_info.device_id must be filled in already
@@ -2093,6 +2171,11 @@ static void setup_oem_data_handler(struct smi_info *smi_info)
 	setup_dell_poweredge_oem_data_handler(smi_info);
 }
 
+static void setup_xaction_handlers(struct smi_info *smi_info)
+{
+	setup_dell_poweredge_bt_xaction_handler(smi_info);
+}
+
 /* Returns 0 if initialized, or negative on an error. */
 static int init_one_smi(int intf_num, struct smi_info **smi)
 {
@@ -2188,6 +2271,7 @@ static int init_one_smi(int intf_num, struct smi_info **smi)
 		goto out_err;
 
 	setup_oem_data_handler(new_smi);
+	setup_xaction_handlers(new_smi);
 
 	/* Try to claim any interrupts. */
 	new_smi->irq_setup(new_smi);