Re: [PATCH v8 1/3] ipmi: ssif_bmc: Add SSIF BMC driver

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On 17/06/2022 03:47, Christophe JAILLET wrote:
Le 15/06/2022 à 11:02, Quan Nguyen a écrit :
The SMBus system interface (SSIF) IPMI BMC driver can be used to perform
in-band IPMI communication with their host in management (BMC) side.

Thanks Dan for the copy_from_user() fix in the link below.

Link: https://lore.kernel.org/linux-arm-kernel/20220310114119.13736-4-quan-shex6MNQR2J/SfDzf78azzKzEDxYleXD@xxxxxxxxxxxxxxxx/ Signed-off-by: Quan Nguyen <quan-shex6MNQR2J/SfDzf78azzKzEDxYleXD@xxxxxxxxxxxxxxxx>
---

Hi,

a few nitpick below

[...]

diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
new file mode 100644
index 000000000000..0bfd4b9bbaf1
--- /dev/null
+++ b/drivers/char/ipmi/ssif_bmc.c
@@ -0,0 +1,880 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * The driver for BMC side of SSIF interface
+ *
+ * Copyright (c) 2022, Ampere Computing LLC
+ *
+ */
+
+#include <linux/i2c.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+#include <linux/jiffies.h>
+#include <linux/ipmi_ssif_bmc.h>
+
+#define DEVICE_NAME                             "ipmi-ssif-host"
+
+#define GET_8BIT_ADDR(addr_7bit)                (((addr_7bit) << 1) & 0xff)
+
+/* A standard SMBus Transaction is limited to 32 data bytes */
+#define MAX_PAYLOAD_PER_TRANSACTION             32
+/* Transaction includes the address, the command, the length and the PEC byte */ +#define MAX_TRANSACTION (MAX_PAYLOAD_PER_TRANSACTION + 4)
+
+#define MAX_IPMI_DATA_PER_START_TRANSACTION     30
+#define MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION    31
+
+#define SSIF_IPMI_SINGLEPART_WRITE              0x2
+#define SSIF_IPMI_SINGLEPART_READ               0x3
+#define SSIF_IPMI_MULTIPART_WRITE_START         0x6
+#define SSIF_IPMI_MULTIPART_WRITE_MIDDLE        0x7
+#define SSIF_IPMI_MULTIPART_WRITE_END           0x8
+#define SSIF_IPMI_MULTIPART_READ_START          0x3
+#define SSIF_IPMI_MULTIPART_READ_MIDDLE         0x9
+
+/*
+ * IPMI 2.0 Spec, section 12.7 SSIF Timing,
+ * Request-to-Response Time is T6max(250ms) - T1max(20ms) - 3ms = 227ms
+ * Recover ssif_bmc from busy state if it takes up to 500ms
+ */
+#define RESPONSE_TIMEOUT                        500 /* ms */
+
+struct ssif_part_buffer {
+    u8 address;
+    u8 smbus_cmd;
+    u8 length;
+    u8 payload[MAX_PAYLOAD_PER_TRANSACTION];
+    u8 pec;
+    u8 index;
+};
+
+/*
+ * SSIF internal states:
+ *   SSIF_READY         0x00 : Ready state
+ *   SSIF_START         0x01 : Start smbus transaction
+ *   SSIF_SMBUS_CMD     0x02 : Received SMBus command
+ *   SSIF_REQ_RECVING   0x03 : Receiving request
+ *   SSIF_RES_SENDING   0x04 : Sending response
+ *   SSIF_BAD_SMBUS     0x05 : Bad SMbus transaction

If these states are related to the enum just below, s/SSIF_BAD_SMBUS/SSIF_ABORTING/ + description update?

Thank you for this catch.
Will fix in new version.

+ */
+enum ssif_state {
+    SSIF_READY,
+    SSIF_START,
+    SSIF_SMBUS_CMD,
+    SSIF_REQ_RECVING,
+    SSIF_RES_SENDING,
+    SSIF_ABORTING,
+    SSIF_STATE_MAX
+};
+

[...]

+static int ssif_bmc_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+    struct ssif_bmc_ctx *ssif_bmc;
+    int ret;
+
+    ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc), GFP_KERNEL);
+    if (!ssif_bmc)
+        return -ENOMEM;
+
+    spin_lock_init(&ssif_bmc->lock);
+
+    init_waitqueue_head(&ssif_bmc->wait_queue);
+    ssif_bmc->request_available = false;
+    ssif_bmc->response_in_progress = false;
+    ssif_bmc->busy = false;
+    ssif_bmc->response_timer_inited = false;
+
+    /* Register misc device interface */
+    ssif_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
+    ssif_bmc->miscdev.name = DEVICE_NAME;
+    ssif_bmc->miscdev.fops = &ssif_bmc_fops;
+    ssif_bmc->miscdev.parent = &client->dev;
+    ret = misc_register(&ssif_bmc->miscdev);
+    if (ret)
+        goto out;

Could be "return ret;"
(see below)

Will change to "return ret;" in next version
+
+    ssif_bmc->client = client;
+    ssif_bmc->client->flags |= I2C_CLIENT_SLAVE;
+
+    /* Register I2C slave */
+    i2c_set_clientdata(client, ssif_bmc);
+    ret = i2c_slave_register(client, ssif_bmc_cb);
+    if (ret) {
+        misc_deregister(&ssif_bmc->miscdev);
+        goto out;
+    }
+
+    return 0;
+out:
+    devm_kfree(&client->dev, ssif_bmc);

This looks useless to me. The whole error handling path could be removed, or updated to only have the "misc_deregister()" above.


Will rewrite as:

    /* Register I2C slave */
    i2c_set_clientdata(client, ssif_bmc);
    ret = i2c_slave_register(client, ssif_bmc_cb);
    if (ret)
        misc_deregister(&ssif_bmc->miscdev);

    return ret;

Thanks for the review.
- Quan




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