<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>blk_stack_limits</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The Linux Kernel API" /><link rel="up" href="ch14.html" title="Chapter 14. Block Devices" /><link rel="prev" href="re554.html" title="blk_queue_stack_limits" /><link rel="next" href="re556.html" title="bdev_stack_limits" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>blk_stack_limits</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re554.html">Prev</a> </td><th width="60%" align="center">Chapter 14. Block Devices</th><td width="20%" align="right"> <a accesskey="n" href="re556.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="blk_stack_limits"><a id="API-blk-stack-limits"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>blk_stack_limits — adjust queue_limits for stacked devices </p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">blk_stack_limits </b>(</code></td><td>struct queue_limits * <var class="pdparam">t</var>, </td></tr><tr><td> </td><td>struct queue_limits * <var class="pdparam">b</var>, </td></tr><tr><td> </td><td>sector_t <var class="pdparam">start</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2704268"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>t</code></em></span></dt><dd><p> the stacking driver limits (top device) </p></dd><dt><span class="term"><em class="parameter"><code>b</code></em></span></dt><dd><p> the underlying queue limits (bottom, component device) </p></dd><dt><span class="term"><em class="parameter"><code>start</code></em></span></dt><dd><p> first data sector within component device </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2704330"></a><h2>Description</h2><p> This function is used by stacking drivers like MD and DM to ensure that all component devices have compatible block sizes and alignments. The stacking driver must provide a queue_limits struct (top) and then iteratively call the stacking function for all component (bottom) devices. The stacking function will attempt to combine the values and ensure proper alignment. </p><p> Returns 0 if the top and bottom queue_limits are compatible. The top device's block sizes and alignment offsets may be adjusted to ensure alignment with the bottom device. If no compatible sizes and alignments exist, -1 is returned and the resulting top queue_limits will have the misaligned flag set to indicate that the alignment_offset is undefined. </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re554.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch14.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re556.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>blk_queue_stack_limits</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>bdev_stack_limits</span></td></tr></table></div></body></html>