linux-kernel - Re: [PATCH v2 1/2] Bluetooth: Add support for devcoredump

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Date:   Fri, 24 Jun 2022 08:49:45 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Manish Mandlik <mmandlik@...gle.com>,
        Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
Cc:     marcel@...tmann.org, luiz.dentz@...il.com,
        chromeos-bluetooth-upstreaming@...omium.org,
        linux-bluetooth@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 1/2] Bluetooth: Add support for devcoredump

Dear Manish, dear Abhishek,


Thank you for the patch.

Am 23.06.22 um 21:37 schrieb Manish Mandlik:
> From: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> 
> Add devcoredump APIs to hci core so that drivers only have to provide
> the dump skbs instead of managing the synchronization and timeouts.
> 
> The devcoredump APIs should be used in the following manner:
>   - hci_devcoredump_init is called to allocate the dump.
>   - hci_devcoredump_append is called to append any skbs with dump data
>     OR hci_devcoredump_append_pattern is called to insert a pattern.
>   - hci_devcoredump_complete is called when all dump packets have been
>     sent OR hci_devcoredump_abort is called to indicate an error and
>     cancel an ongoing dump collection.
> 
> The high level APIs just prepare some skbs with the appropriate data and
> queue it for the dump to process. Packets part of the crashdump can be
> intercepted in the driver in interrupt context and forwarded directly to
> the devcoredump APIs.
> 
> Internally, there are 5 states for the dump: idle, active, complete,
> abort and timeout. A devcoredump will only be in active state after it
> has been initialized. Once active, it accepts data to be appended,
> patterns to be inserted (i.e. memset) and a completion event or an abort
> event to generate a devcoredump. The timeout is initialized at the same
> time the dump is initialized (defaulting to 10s) and will be cleared
> either when the timeout occurs or the dump is complete or aborted.

Do you have a usage example, how this can be used fro userspace?

> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> Signed-off-by: Manish Mandlik <mmandlik@...gle.com>
> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> ---
> 
> Changes in v2:
> - Move hci devcoredump implementation to new files
> - Move dump queue and dump work to hci_devcoredump struct
> - Add CONFIG_DEV_COREDUMP conditional compile
> 
>   include/net/bluetooth/coredump.h | 109 +++++++
>   include/net/bluetooth/hci_core.h |   5 +
>   net/bluetooth/Makefile           |   2 +
>   net/bluetooth/coredump.c         | 504 +++++++++++++++++++++++++++++++
>   net/bluetooth/hci_core.c         |   9 +
>   net/bluetooth/hci_sync.c         |   2 +
>   6 files changed, 631 insertions(+)
>   create mode 100644 include/net/bluetooth/coredump.h
>   create mode 100644 net/bluetooth/coredump.c
> 
> diff --git a/include/net/bluetooth/coredump.h b/include/net/bluetooth/coredump.h
> new file mode 100644
> index 000000000000..73601c409c6e
> --- /dev/null
> +++ b/include/net/bluetooth/coredump.h
> @@ -0,0 +1,109 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022 Google Corporation
> + */
> +
> +#ifndef __COREDUMP_H
> +#define __COREDUMP_H
> +
> +#define DEVCOREDUMP_TIMEOUT	msecs_to_jiffies(10000)	/* 10 sec */
> +
> +typedef int  (*dmp_hdr_t)(struct hci_dev *hdev, char *buf, size_t size);
> +typedef void (*notify_change_t)(struct hci_dev *hdev, int state);
> +
> +/* struct hci_devcoredump - Devcoredump state
> + *
> + * @supported: Indicates if FW dump collection is supported by driver
> + * @state: Current state of dump collection
> + * @alloc_size: Total size of the dump
> + * @head: Start of the dump
> + * @tail: Pointer to current end of dump
> + * @end: head + alloc_size for easy comparisons
> + *
> + * @dump_q: Dump queue for state machine to process
> + * @dump_rx: Devcoredump state machine work
> + * @dump_timeout: Devcoredump timeout work
> + *
> + * @dmp_hdr: Create a dump header to identify controller/fw/driver info
> + * @notify_change: Notify driver when devcoredump state has changed
> + */
> +struct hci_devcoredump {
> +	bool		supported;
> +
> +	enum devcoredump_state {
> +		HCI_DEVCOREDUMP_IDLE,
> +		HCI_DEVCOREDUMP_ACTIVE,
> +		HCI_DEVCOREDUMP_DONE,
> +		HCI_DEVCOREDUMP_ABORT,
> +		HCI_DEVCOREDUMP_TIMEOUT
> +	} state;
> +
> +	u32		alloc_size;

As it’s not packed, why specify the length? Just use size_t or `unsigned 
int`?

[…]


Kind regards,

Paul