add boot partition size

hc

2023-12-11 d2ccde1c8e90d38cee87a1b0309ad2827f3fd30d

 kernel/Documentation/trace/stm.rst
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+.. SPDX-License-Identifier: GPL-2.0
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+
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 ===================
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 System Trace Module
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 ===================
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 have a name (string identifier) and a range of masters and channels
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 associated with it, located in "stp-policy" subsystem directory in
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 configfs. The topmost directory's name (the policy) is formatted as
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-the STM device name to which this policy applies and and arbitrary
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-string identifier separated by a stop. From the examle above, a rule
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+the STM device name to which this policy applies and an arbitrary
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+string identifier separated by a stop. From the example above, a rule
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 may look like this::
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 	$ ls /config/stp-policy/dummy_stm.my-policy/user
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 be used for trace sources with the id string of "user/dummy".
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 Trace sources have to open the stm class device's node and write their
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-trace data into its file descriptor. In order to identify themselves
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-to the policy, they need to do a STP_POLICY_ID_SET ioctl on this file
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-descriptor providing their id string. Otherwise, they will be
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-automatically allocated a master/channel pair upon first write to this
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-file descriptor according to the "default" rule of the policy, if such
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-exists.
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+trace data into its file descriptor.
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+
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+In order to find an appropriate policy node for a given trace source,
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+several mechanisms can be used. First, a trace source can explicitly
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+identify itself by calling an STP_POLICY_ID_SET ioctl on the character
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+device's file descriptor, providing their id string, before they write
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+any data there. Secondly, if they chose not to perform the explicit
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+identification (because you may not want to patch existing software
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+to do this), they can just start writing the data, at which point the
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+stm core will try to find a policy node with the name matching the
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+task's name (e.g., "syslogd") and if one exists, it will be used.
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+Thirdly, if the task name can't be found among the policy nodes, the
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+catch-all entry "default" will be used, if it exists. This entry also
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+needs to be created and configured by the system administrator or
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+whatever tools are taking care of the policy configuration. Finally,
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+if all the above steps failed, the write() to an stm file descriptor
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+will return a error (EINVAL).
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+
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+Previously, if no policy nodes were found for a trace source, the stm
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+class would silently fall back to allocating the first available
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+contiguous range of master/channels from the beginning of the device's
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+master/channel range. The new requirement for a policy node to exist
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+will help programmers and sysadmins identify gaps in configuration
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+and have better control over the un-identified sources.
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 Some STM devices may allow direct mapping of the channel mmio regions
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 to userspace for zero-copy writing. One mappable page (in terms of
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 there's a node in the root of the policy directory that matches the
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 stm_source device's name (for example, "console"), this node will be
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 used to allocate master and channel numbers. If there's no such policy
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-node, the stm core will pick the first contiguous chunk of channels
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-within the first available master. Note that the node must exist
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-before the stm_source device is connected to its stm device.
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+node, the stm core will use the catch-all entry "default", if one
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+exists. If neither policy nodes exist, the write() to stm_source_link
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+will return an error.
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 stm_console
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 ===========